Merge pull request 'MyFSIO v0.1.9 Release' (#10) from next into main

Reviewed-on: #10

app/__init__.py

@@ -45,7 +45,6 @@ def _migrate_config_file(active_path: Path, legacy_paths: List[Path]) -> Path:
             try:
                 shutil.move(str(legacy_path), str(active_path))
             except OSError:
-                # Fall back to copy + delete if move fails (e.g., cross-device)
                 shutil.copy2(legacy_path, active_path)
                 try:
                     legacy_path.unlink(missing_ok=True)
@@ -101,32 +100,28 @@ def create_app(
     bucket_policies = BucketPolicyStore(Path(app.config["BUCKET_POLICY_PATH"]))
     secret_store = EphemeralSecretStore(default_ttl=app.config.get("SECRET_TTL_SECONDS", 300))
     
-    # Initialize Replication components
-    # Store config files in the system config directory for consistency
     storage_root = Path(app.config["STORAGE_ROOT"])
     config_dir = storage_root / ".myfsio.sys" / "config"
     config_dir.mkdir(parents=True, exist_ok=True)
     
-    # Define paths with migration from legacy locations
     connections_path = _migrate_config_file(
         active_path=config_dir / "connections.json",
         legacy_paths=[
-            storage_root / ".myfsio.sys" / "connections.json",  # Previous location
+            storage_root / ".myfsio.sys" / "connections.json",
-            storage_root / ".connections.json",  # Original legacy location
+            storage_root / ".connections.json",
         ],
     )
     replication_rules_path = _migrate_config_file(
         active_path=config_dir / "replication_rules.json",
         legacy_paths=[
-            storage_root / ".myfsio.sys" / "replication_rules.json",  # Previous location
+            storage_root / ".myfsio.sys" / "replication_rules.json",
-            storage_root / ".replication_rules.json",  # Original legacy location
+            storage_root / ".replication_rules.json",
         ],
     )
     
     connections = ConnectionStore(connections_path)
     replication = ReplicationManager(storage, connections, replication_rules_path)
     
-    # Initialize encryption and KMS
     encryption_config = {
         "encryption_enabled": app.config.get("ENCRYPTION_ENABLED", False),
         "encryption_master_key_path": app.config.get("ENCRYPTION_MASTER_KEY_PATH"),
@@ -141,7 +136,6 @@ def create_app(
         kms_manager = KMSManager(kms_keys_path, kms_master_key_path)
         encryption_manager.set_kms_provider(kms_manager)
 
-    # Wrap storage with encryption layer if encryption is enabled
     if app.config.get("ENCRYPTION_ENABLED", False):
         from .encrypted_storage import EncryptedObjectStorage
         storage = EncryptedObjectStorage(storage, encryption_manager)
@@ -177,13 +171,22 @@ def create_app(
 
     @app.template_filter("timestamp_to_datetime")
     def timestamp_to_datetime(value: float) -> str:
-        """Format Unix timestamp as human-readable datetime."""
+        """Format Unix timestamp as human-readable datetime in configured timezone."""
-        from datetime import datetime
+        from datetime import datetime, timezone as dt_timezone
+        from zoneinfo import ZoneInfo
         if not value:
             return "Never"
         try:
-            dt = datetime.fromtimestamp(value)
+            dt_utc = datetime.fromtimestamp(value, dt_timezone.utc)
-            return dt.strftime("%Y-%m-%d %H:%M:%S")
+            display_tz = app.config.get("DISPLAY_TIMEZONE", "UTC")
+            if display_tz and display_tz != "UTC":
+                try:
+                    tz = ZoneInfo(display_tz)
+                    dt_local = dt_utc.astimezone(tz)
+                    return dt_local.strftime("%Y-%m-%d %H:%M:%S")
+                except (KeyError, ValueError):
+                    pass 
+            return dt_utc.strftime("%Y-%m-%d %H:%M:%S UTC")
         except (ValueError, OSError):
             return "Unknown"
 
@@ -244,7 +247,7 @@ def _configure_cors(app: Flask) -> None:
 class _RequestContextFilter(logging.Filter):
     """Inject request-specific attributes into log records."""
 
-    def filter(self, record: logging.LogRecord) -> bool:  # pragma: no cover - simple boilerplate
+    def filter(self, record: logging.LogRecord) -> bool:  
         if has_request_context():
             record.request_id = getattr(g, "request_id", "-")
             record.path = request.path

app/bucket_policies.py

@@ -188,7 +188,6 @@ class BucketPolicyStore:
         except FileNotFoundError:
             return None
 
-    # ------------------------------------------------------------------
     def evaluate(
         self,
         access_key: Optional[str],
@@ -229,7 +228,6 @@ class BucketPolicyStore:
         self._policies.pop(bucket, None)
         self._persist()
 
-    # ------------------------------------------------------------------
     def _load(self) -> None:
         try:
             content = self.policy_path.read_text(encoding='utf-8')

app/config.py

@@ -73,6 +73,7 @@ class AppConfig:
     kms_enabled: bool
     kms_keys_path: Path
     default_encryption_algorithm: str
+    display_timezone: str
 
     @classmethod
     def from_env(cls, overrides: Optional[Dict[str, Any]] = None) -> "AppConfig":
@@ -153,15 +154,15 @@ class AppConfig:
         cors_allow_headers = _csv(str(_get("CORS_ALLOW_HEADERS", "*")), ["*"])
         cors_expose_headers = _csv(str(_get("CORS_EXPOSE_HEADERS", "*")), ["*"])
         session_lifetime_days = int(_get("SESSION_LIFETIME_DAYS", 30))
-        bucket_stats_cache_ttl = int(_get("BUCKET_STATS_CACHE_TTL", 60))  # Default 60 seconds
+        bucket_stats_cache_ttl = int(_get("BUCKET_STATS_CACHE_TTL", 60)) 
         
-        # Encryption settings
         encryption_enabled = str(_get("ENCRYPTION_ENABLED", "0")).lower() in {"1", "true", "yes", "on"}
         encryption_keys_dir = storage_root / ".myfsio.sys" / "keys"
         encryption_master_key_path = Path(_get("ENCRYPTION_MASTER_KEY_PATH", encryption_keys_dir / "master.key")).resolve()
         kms_enabled = str(_get("KMS_ENABLED", "0")).lower() in {"1", "true", "yes", "on"}
         kms_keys_path = Path(_get("KMS_KEYS_PATH", encryption_keys_dir / "kms_keys.json")).resolve()
         default_encryption_algorithm = str(_get("DEFAULT_ENCRYPTION_ALGORITHM", "AES256"))
+        display_timezone = str(_get("DISPLAY_TIMEZONE", "UTC"))
 
         return cls(storage_root=storage_root,
                    max_upload_size=max_upload_size,
@@ -196,7 +197,8 @@ class AppConfig:
                    encryption_master_key_path=encryption_master_key_path,
                    kms_enabled=kms_enabled,
                    kms_keys_path=kms_keys_path,
-                   default_encryption_algorithm=default_encryption_algorithm)
+                   default_encryption_algorithm=default_encryption_algorithm,
+                   display_timezone=display_timezone)
 
     def validate_and_report(self) -> list[str]:
         """Validate configuration and return a list of warnings/issues.
@@ -206,7 +208,6 @@ class AppConfig:
         """
         issues = []
         
-        # Check if storage_root is writable
         try:
             test_file = self.storage_root / ".write_test"
             test_file.touch()
@@ -214,24 +215,20 @@ class AppConfig:
         except (OSError, PermissionError) as e:
             issues.append(f"CRITICAL: STORAGE_ROOT '{self.storage_root}' is not writable: {e}")
         
-        # Check if storage_root looks like a temp directory
         storage_str = str(self.storage_root).lower()
         if "/tmp" in storage_str or "\\temp" in storage_str or "appdata\\local\\temp" in storage_str:
             issues.append(f"WARNING: STORAGE_ROOT '{self.storage_root}' appears to be a temporary directory. Data may be lost on reboot!")
         
-        # Check if IAM config path is under storage_root
         try:
             self.iam_config_path.relative_to(self.storage_root)
         except ValueError:
             issues.append(f"WARNING: IAM_CONFIG '{self.iam_config_path}' is outside STORAGE_ROOT '{self.storage_root}'. Consider setting IAM_CONFIG explicitly or ensuring paths are aligned.")
         
-        # Check if bucket policy path is under storage_root
         try:
             self.bucket_policy_path.relative_to(self.storage_root)
         except ValueError:
             issues.append(f"WARNING: BUCKET_POLICY_PATH '{self.bucket_policy_path}' is outside STORAGE_ROOT '{self.storage_root}'. Consider setting BUCKET_POLICY_PATH explicitly.")
         
-        # Check if log path is writable
         try:
             self.log_path.parent.mkdir(parents=True, exist_ok=True)
             test_log = self.log_path.parent / ".write_test"
@@ -240,26 +237,22 @@ class AppConfig:
         except (OSError, PermissionError) as e:
             issues.append(f"WARNING: Log directory '{self.log_path.parent}' is not writable: {e}")
         
-        # Check log path location
         log_str = str(self.log_path).lower()
         if "/tmp" in log_str or "\\temp" in log_str or "appdata\\local\\temp" in log_str:
             issues.append(f"WARNING: LOG_DIR '{self.log_path.parent}' appears to be a temporary directory. Logs may be lost on reboot!")
         
-        # Check if encryption keys path is under storage_root (when encryption is enabled)
         if self.encryption_enabled:
             try:
                 self.encryption_master_key_path.relative_to(self.storage_root)
             except ValueError:
                 issues.append(f"WARNING: ENCRYPTION_MASTER_KEY_PATH '{self.encryption_master_key_path}' is outside STORAGE_ROOT. Ensure proper backup procedures.")
         
-        # Check if KMS keys path is under storage_root (when KMS is enabled)
         if self.kms_enabled:
             try:
                 self.kms_keys_path.relative_to(self.storage_root)
             except ValueError:
                 issues.append(f"WARNING: KMS_KEYS_PATH '{self.kms_keys_path}' is outside STORAGE_ROOT. Ensure proper backup procedures.")
         
-        # Warn about production settings
         if self.secret_key == "dev-secret-key":
             issues.append("WARNING: Using default SECRET_KEY. Set SECRET_KEY environment variable for production.")
         
@@ -330,4 +323,5 @@ class AppConfig:
             "KMS_ENABLED": self.kms_enabled,
             "KMS_KEYS_PATH": str(self.kms_keys_path),
             "DEFAULT_ENCRYPTION_ALGORITHM": self.default_encryption_algorithm,
+            "DISPLAY_TIMEZONE": self.display_timezone,
         }

app/iam.py

@@ -6,7 +6,7 @@ import math
 import secrets
 from collections import deque
 from dataclasses import dataclass
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from pathlib import Path
 from typing import Any, Deque, Dict, Iterable, List, Optional, Sequence, Set
 
@@ -125,7 +125,6 @@ class IamService:
         except OSError:
             pass
 
-    # ---------------------- authz helpers ----------------------
     def authenticate(self, access_key: str, secret_key: str) -> Principal:
         self._maybe_reload()
         access_key = (access_key or "").strip()
@@ -149,7 +148,7 @@ class IamService:
             return
         attempts = self._failed_attempts.setdefault(access_key, deque())
         self._prune_attempts(attempts)
-        attempts.append(datetime.now())
+        attempts.append(datetime.now(timezone.utc))
 
     def _clear_failed_attempts(self, access_key: str) -> None:
         if not access_key:
@@ -157,7 +156,7 @@ class IamService:
         self._failed_attempts.pop(access_key, None)
 
     def _prune_attempts(self, attempts: Deque[datetime]) -> None:
-        cutoff = datetime.now() - self.auth_lockout_window
+        cutoff = datetime.now(timezone.utc) - self.auth_lockout_window
         while attempts and attempts[0] < cutoff:
             attempts.popleft()
 
@@ -178,7 +177,7 @@ class IamService:
         if len(attempts) < self.auth_max_attempts:
             return 0
         oldest = attempts[0]
-        elapsed = (datetime.now() - oldest).total_seconds()
+        elapsed = (datetime.now(timezone.utc) - oldest).total_seconds()
         return int(max(0, self.auth_lockout_window.total_seconds() - elapsed))
 
     def principal_for_key(self, access_key: str) -> Principal:
@@ -218,7 +217,6 @@ class IamService:
                 return True
         return False
 
-    # ---------------------- management helpers ----------------------
     def list_users(self) -> List[Dict[str, Any]]:
         listing: List[Dict[str, Any]] = []
         for access_key, record in self._users.items():
@@ -291,7 +289,6 @@ class IamService:
         self._save()
         self._load()
 
-    # ---------------------- config helpers ----------------------
     def _load(self) -> None:
         try:
             self._last_load_time = self.config_path.stat().st_mtime
@@ -337,7 +334,6 @@ class IamService:
         except (OSError, PermissionError) as e:
             raise IamError(f"Cannot save IAM config: {e}")
 
-    # ---------------------- insight helpers ----------------------
     def config_summary(self) -> Dict[str, Any]:
         return {
             "path": str(self.config_path),

app/kms_api.py

@@ -33,9 +33,6 @@ def _encryption():
 def _error_response(code: str, message: str, status: int) -> tuple[Dict[str, Any], int]:
     return {"__type": code, "message": message}, status
 
-
-# ---------------------- Key Management ----------------------
-
 @kms_api_bp.route("/keys", methods=["GET", "POST"])
 @limiter.limit("30 per minute")
 def list_or_create_keys():
@@ -65,7 +62,6 @@ def list_or_create_keys():
         except EncryptionError as exc:
             return _error_response("KMSInternalException", str(exc), 400)
     
-    # GET - List keys
     keys = kms.list_keys()
     return jsonify({
         "Keys": [{"KeyId": k.key_id, "KeyArn": k.arn} for k in keys],
@@ -96,7 +92,6 @@ def get_or_delete_key(key_id: str):
         except EncryptionError as exc:
             return _error_response("NotFoundException", str(exc), 404)
     
-    # GET
     key = kms.get_key(key_id)
     if not key:
         return _error_response("NotFoundException", f"Key not found: {key_id}", 404)
@@ -149,9 +144,6 @@ def disable_key(key_id: str):
     except EncryptionError as exc:
         return _error_response("NotFoundException", str(exc), 404)
 
-
-# ---------------------- Encryption Operations ----------------------
-
 @kms_api_bp.route("/encrypt", methods=["POST"])
 @limiter.limit("60 per minute")
 def encrypt_data():
@@ -251,7 +243,6 @@ def generate_data_key():
     try:
         plaintext_key, encrypted_key = kms.generate_data_key(key_id, context)
         
-        # Trim key if AES_128 requested
         if key_spec == "AES_128":
             plaintext_key = plaintext_key[:16]
         
@@ -322,10 +313,7 @@ def re_encrypt():
         return _error_response("ValidationException", "CiphertextBlob must be base64 encoded", 400)
     
     try:
-        # First decrypt, get source key id
         plaintext, source_key_id = kms.decrypt(ciphertext, source_context)
-        
-        # Re-encrypt with destination key
         new_ciphertext = kms.encrypt(destination_key_id, plaintext, destination_context)
         
         return jsonify({
@@ -365,9 +353,6 @@ def generate_random():
     except EncryptionError as exc:
         return _error_response("ValidationException", str(exc), 400)
 
-
-# ---------------------- Client-Side Encryption Helpers ----------------------
-
 @kms_api_bp.route("/client/generate-key", methods=["POST"])
 @limiter.limit("30 per minute")
 def generate_client_key():
@@ -427,9 +412,6 @@ def client_decrypt():
     except Exception as exc:
         return _error_response("DecryptionError", str(exc), 400)
 
-
-# ---------------------- Encryption Materials for S3 Client-Side Encryption ----------------------
-
 @kms_api_bp.route("/materials/<key_id>", methods=["POST"])
 @limiter.limit("60 per minute")
 def get_encryption_materials(key_id: str):

app/replication.py

@@ -9,7 +9,7 @@ import time
 from concurrent.futures import ThreadPoolExecutor
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import Dict, Optional
+from typing import Any, Dict, Optional
 
 import boto3
 from botocore.config import Config
@@ -22,18 +22,51 @@ from .storage import ObjectStorage, StorageError
 logger = logging.getLogger(__name__)
 
 REPLICATION_USER_AGENT = "S3ReplicationAgent/1.0"
+REPLICATION_CONNECT_TIMEOUT = 5
+REPLICATION_READ_TIMEOUT = 30
+STREAMING_THRESHOLD_BYTES = 10 * 1024 * 1024  # 10 MiB - use streaming for larger files
 
 REPLICATION_MODE_NEW_ONLY = "new_only"
 REPLICATION_MODE_ALL = "all"
 
 
+def _create_s3_client(connection: RemoteConnection, *, health_check: bool = False) -> Any:
+    """Create a boto3 S3 client for the given connection.
+
+    Args:
+        connection: Remote S3 connection configuration
+        health_check: If True, use minimal retries for quick health checks
+
+    Returns:
+        Configured boto3 S3 client
+    """
+    config = Config(
+        user_agent_extra=REPLICATION_USER_AGENT,
+        connect_timeout=REPLICATION_CONNECT_TIMEOUT,
+        read_timeout=REPLICATION_READ_TIMEOUT,
+        retries={'max_attempts': 1 if health_check else 2},
+        signature_version='s3v4',
+        s3={'addressing_style': 'path'},
+        request_checksum_calculation='when_required',
+        response_checksum_validation='when_required',
+    )
+    return boto3.client(
+        "s3",
+        endpoint_url=connection.endpoint_url,
+        aws_access_key_id=connection.access_key,
+        aws_secret_access_key=connection.secret_key,
+        region_name=connection.region or 'us-east-1',
+        config=config,
+    )
+
+
 @dataclass
 class ReplicationStats:
     """Statistics for replication operations - computed dynamically."""
-    objects_synced: int = 0          # Objects that exist in both source and destination
+    objects_synced: int = 0
-    objects_pending: int = 0         # Objects in source but not in destination
+    objects_pending: int = 0
-    objects_orphaned: int = 0        # Objects in destination but not in source (will be deleted)
+    objects_orphaned: int = 0
-    bytes_synced: int = 0            # Total bytes synced to destination
+    bytes_synced: int = 0      
     last_sync_at: Optional[float] = None
     last_sync_key: Optional[str] = None
     
@@ -83,7 +116,6 @@ class ReplicationRule:
     @classmethod
     def from_dict(cls, data: dict) -> "ReplicationRule":
         stats_data = data.pop("stats", {})
-        # Handle old rules without mode/created_at
         if "mode" not in data:
             data["mode"] = REPLICATION_MODE_NEW_ONLY
         if "created_at" not in data:
@@ -101,8 +133,19 @@ class ReplicationManager:
         self._rules: Dict[str, ReplicationRule] = {}
         self._stats_lock = threading.Lock()
         self._executor = ThreadPoolExecutor(max_workers=4, thread_name_prefix="ReplicationWorker")
+        self._shutdown = False
         self.reload_rules()
 
+    def shutdown(self, wait: bool = True) -> None:
+        """Shutdown the replication executor gracefully.
+
+        Args:
+            wait: If True, wait for pending tasks to complete
+        """
+        self._shutdown = True
+        self._executor.shutdown(wait=wait)
+        logger.info("Replication manager shut down")
+
     def reload_rules(self) -> None:
         if not self.rules_path.exists():
             self._rules = {}
@@ -121,6 +164,20 @@ class ReplicationManager:
         with open(self.rules_path, "w") as f:
             json.dump(data, f, indent=2)
 
+    def check_endpoint_health(self, connection: RemoteConnection) -> bool:
+        """Check if a remote endpoint is reachable and responsive.
+
+        Returns True if endpoint is healthy, False otherwise.
+        Uses short timeouts to prevent blocking.
+        """
+        try:
+            s3 = _create_s3_client(connection, health_check=True)
+            s3.list_buckets()
+            return True
+        except Exception as e:
+            logger.warning(f"Endpoint health check failed for {connection.name} ({connection.endpoint_url}): {e}")
+            return False
+
     def get_rule(self, bucket_name: str) -> Optional[ReplicationRule]:
         return self._rules.get(bucket_name)
 
@@ -151,21 +208,13 @@ class ReplicationManager:
         
         connection = self.connections.get(rule.target_connection_id)
         if not connection:
-            return rule.stats  # Return cached stats if connection unavailable
+            return rule.stats
         
         try:
-            # Get source objects
             source_objects = self.storage.list_objects_all(bucket_name)
             source_keys = {obj.key: obj.size for obj in source_objects}
 
-            # Get destination objects
+            s3 = _create_s3_client(connection)
-            s3 = boto3.client(
-                "s3",
-                endpoint_url=connection.endpoint_url,
-                aws_access_key_id=connection.access_key,
-                aws_secret_access_key=connection.secret_key,
-                region_name=connection.region,
-            )
 
             dest_keys = set()
             bytes_synced = 0
@@ -178,24 +227,18 @@ class ReplicationManager:
                             bytes_synced += obj.get('Size', 0)
             except ClientError as e:
                 if e.response['Error']['Code'] == 'NoSuchBucket':
-                    # Destination bucket doesn't exist yet
                     dest_keys = set()
                 else:
                     raise
             
-            # Compute stats
+            synced = source_keys.keys() & dest_keys  
-            synced = source_keys.keys() & dest_keys  # Objects in both
+            orphaned = dest_keys - source_keys.keys() 
-            orphaned = dest_keys - source_keys.keys()  # In dest but not source
             
-            # For "new_only" mode, we can't determine pending since we don't know
-            # which objects existed before replication was enabled. Only "all" mode
-            # should show pending (objects that should be replicated but aren't yet).
             if rule.mode == REPLICATION_MODE_ALL:
-                pending = source_keys.keys() - dest_keys  # In source but not dest
+                pending = source_keys.keys() - dest_keys 
             else:
-                pending = set()  # New-only mode: don't show pre-existing as pending
+                pending = set()
             
-            # Update cached stats with computed values
             rule.stats.objects_synced = len(synced)
             rule.stats.objects_pending = len(pending)
             rule.stats.objects_orphaned = len(orphaned)
@@ -205,7 +248,7 @@ class ReplicationManager:
             
         except (ClientError, StorageError) as e:
             logger.error(f"Failed to compute sync status for {bucket_name}: {e}")
-            return rule.stats  # Return cached stats on error
+            return rule.stats
     
     def replicate_existing_objects(self, bucket_name: str) -> None:
         """Trigger replication for all existing objects in a bucket."""
@@ -218,6 +261,10 @@ class ReplicationManager:
             logger.warning(f"Cannot replicate existing objects: Connection {rule.target_connection_id} not found")
             return
         
+        if not self.check_endpoint_health(connection):
+            logger.warning(f"Cannot replicate existing objects: Endpoint {connection.name} ({connection.endpoint_url}) is not reachable")
+            return
+        
         try:
             objects = self.storage.list_objects_all(bucket_name)
             logger.info(f"Starting replication of {len(objects)} existing objects from {bucket_name}")
@@ -233,13 +280,7 @@ class ReplicationManager:
             raise ValueError(f"Connection {connection_id} not found")
 
         try:
-            s3 = boto3.client(
+            s3 = _create_s3_client(connection)
-                "s3",
-                endpoint_url=connection.endpoint_url,
-                aws_access_key_id=connection.access_key,
-                aws_secret_access_key=connection.secret_key,
-                region_name=connection.region,
-            )
             s3.create_bucket(Bucket=bucket_name)
         except ClientError as e:
             logger.error(f"Failed to create remote bucket {bucket_name}: {e}")
@@ -255,9 +296,22 @@ class ReplicationManager:
             logger.warning(f"Replication skipped for {bucket_name}/{object_key}: Connection {rule.target_connection_id} not found")
             return
 
+        if not self.check_endpoint_health(connection):
+            logger.warning(f"Replication skipped for {bucket_name}/{object_key}: Endpoint {connection.name} ({connection.endpoint_url}) is not reachable")
+            return
+
         self._executor.submit(self._replicate_task, bucket_name, object_key, rule, connection, action)
 
     def _replicate_task(self, bucket_name: str, object_key: str, rule: ReplicationRule, conn: RemoteConnection, action: str) -> None:
+        if self._shutdown:
+            return
+
+        # Re-check if rule is still enabled (may have been paused after task was submitted)
+        current_rule = self.get_rule(bucket_name)
+        if not current_rule or not current_rule.enabled:
+            logger.debug(f"Replication skipped for {bucket_name}/{object_key}: rule disabled or removed")
+            return
+
         if ".." in object_key or object_key.startswith("/") or object_key.startswith("\\"):
             logger.error(f"Invalid object key in replication (path traversal attempt): {object_key}")
             return
@@ -269,17 +323,8 @@ class ReplicationManager:
             logger.error(f"Object key validation failed in replication: {e}")
             return
 
-        file_size = 0
         try:
-            config = Config(user_agent_extra=REPLICATION_USER_AGENT)
+            s3 = _create_s3_client(conn)
-            s3 = boto3.client(
-                "s3",
-                endpoint_url=conn.endpoint_url,
-                aws_access_key_id=conn.access_key,
-                aws_secret_access_key=conn.secret_key,
-                region_name=conn.region,
-                config=config,
-            )
 
             if action == "delete":
                 try:
@@ -296,54 +341,67 @@ class ReplicationManager:
                 logger.error(f"Source object not found: {bucket_name}/{object_key}")
                 return
 
-            metadata = self.storage.get_object_metadata(bucket_name, object_key)
-
-            extra_args = {}
-            if metadata:
-                extra_args["Metadata"] = metadata
-            
-            # Guess content type to prevent corruption/wrong handling
             content_type, _ = mimetypes.guess_type(path)
             file_size = path.stat().st_size
 
             logger.info(f"Replicating {bucket_name}/{object_key}: Size={file_size}, ContentType={content_type}")
 
-            try:
+            def do_upload() -> None:
-                with path.open("rb") as f:
+                """Upload object using appropriate method based on file size.
-                    s3.put_object(
+
-                        Bucket=rule.target_bucket,
+                For small files (< 10 MiB): Read into memory for simpler handling
-                        Key=object_key,
+                For large files: Use streaming upload to avoid memory issues
-                        Body=f,
+                """
-                        ContentLength=file_size,
+                extra_args = {}
-                        ContentType=content_type or "application/octet-stream",
+                if content_type:
-                        Metadata=metadata or {}
+                    extra_args["ContentType"] = content_type
+
+                if file_size >= STREAMING_THRESHOLD_BYTES:
+                    # Use multipart upload for large files
+                    s3.upload_file(
+                        str(path),
+                        rule.target_bucket,
+                        object_key,
+                        ExtraArgs=extra_args if extra_args else None,
                     )
+                else:
+                    # Read small files into memory
+                    file_content = path.read_bytes()
+                    put_kwargs = {
+                        "Bucket": rule.target_bucket,
+                        "Key": object_key,
+                        "Body": file_content,
+                        **extra_args,
+                    }
+                    s3.put_object(**put_kwargs)
+
+            try:
+                do_upload()
             except (ClientError, S3UploadFailedError) as e:
-                is_no_bucket = False
+                error_code = None
                 if isinstance(e, ClientError):
-                    if e.response['Error']['Code'] == 'NoSuchBucket':
+                    error_code = e.response['Error']['Code']
-                        is_no_bucket = True
                 elif isinstance(e, S3UploadFailedError):
                     if "NoSuchBucket" in str(e):
-                        is_no_bucket = True
+                        error_code = 'NoSuchBucket'
 
-                if is_no_bucket:
+                if error_code == 'NoSuchBucket':
                     logger.info(f"Target bucket {rule.target_bucket} not found. Attempting to create it.")
+                    bucket_ready = False
                     try:
                         s3.create_bucket(Bucket=rule.target_bucket)
-                        # Retry upload
+                        bucket_ready = True
-                        with path.open("rb") as f:
+                        logger.info(f"Created target bucket {rule.target_bucket}")
-                            s3.put_object(
+                    except ClientError as bucket_err:
-                                Bucket=rule.target_bucket,
+                        if bucket_err.response['Error']['Code'] in ('BucketAlreadyExists', 'BucketAlreadyOwnedByYou'):
-                                Key=object_key,
+                            logger.debug(f"Bucket {rule.target_bucket} already exists (created by another thread)")
-                                Body=f,
+                            bucket_ready = True
-                                ContentLength=file_size,
+                        else:
-                                ContentType=content_type or "application/octet-stream",
+                            logger.error(f"Failed to create target bucket {rule.target_bucket}: {bucket_err}")
-                                Metadata=metadata or {}
+                            raise e
-                            )
+
-                    except Exception as create_err:
+                    if bucket_ready:
-                        logger.error(f"Failed to create target bucket {rule.target_bucket}: {create_err}")
+                        do_upload()
-                        raise e # Raise original error
                 else:
                     raise e
 
@@ -354,3 +412,4 @@ class ReplicationManager:
             logger.error(f"Replication failed for {bucket_name}/{object_key}: {e}")
         except Exception:
             logger.exception(f"Unexpected error during replication for {bucket_name}/{object_key}")
+

app/s3_api.py

@@ -1,14 +1,16 @@
 """Flask blueprint exposing a subset of the S3 REST API."""
 from __future__ import annotations
 
+import base64
 import hashlib
 import hmac
+import logging
 import mimetypes
 import re
 import uuid
 from datetime import datetime, timedelta, timezone
-from typing import Any, Dict
+from typing import Any, Dict, Optional
-from urllib.parse import quote, urlencode, urlparse
+from urllib.parse import quote, urlencode, urlparse, unquote
 from xml.etree.ElementTree import Element, SubElement, tostring, fromstring, ParseError
 
 from flask import Blueprint, Response, current_app, jsonify, request, g
@@ -20,10 +22,10 @@ from .iam import IamError, Principal
 from .replication import ReplicationManager
 from .storage import ObjectStorage, StorageError, QuotaExceededError
 
+logger = logging.getLogger(__name__)
+
 s3_api_bp = Blueprint("s3_api", __name__)
 
-
-# ---------------------- helpers ----------------------
 def _storage() -> ObjectStorage:
     return current_app.extensions["object_storage"]
 
@@ -68,9 +70,26 @@ def _get_signature_key(key: str, date_stamp: str, region_name: str, service_name
     return k_signing
 
 
+def _get_canonical_uri(req: Any) -> str:
+    """Get the canonical URI for SigV4 signature verification.
+    
+    AWS SigV4 requires the canonical URI to be URL-encoded exactly as the client
+    sent it. Flask/Werkzeug automatically URL-decodes request.path, so we need
+    to get the raw path from the environ.
+    
+    The canonical URI should have each path segment URL-encoded (with '/' preserved),
+    and the encoding should match what the client used when signing.
+    """
+    raw_uri = req.environ.get('RAW_URI') or req.environ.get('REQUEST_URI')
+    
+    if raw_uri:
+        path = raw_uri.split('?')[0]
+        return path
+    
+    return quote(req.path, safe="/-_.~")
+
+
 def _verify_sigv4_header(req: Any, auth_header: str) -> Principal | None:
-    # Parse Authorization header
-    # AWS4-HMAC-SHA256 Credential=AKIA.../20230101/us-east-1/s3/aws4_request, SignedHeaders=host;x-amz-date, Signature=...
     match = re.match(
         r"AWS4-HMAC-SHA256 Credential=([^/]+)/([^/]+)/([^/]+)/([^/]+)/aws4_request, SignedHeaders=([^,]+), Signature=(.+)",
         auth_header,
@@ -79,17 +98,13 @@ def _verify_sigv4_header(req: Any, auth_header: str) -> Principal | None:
         return None
 
     access_key, date_stamp, region, service, signed_headers_str, signature = match.groups()
-
-    # Get secret key
     secret_key = _iam().get_secret_key(access_key)
     if not secret_key:
         raise IamError("Invalid access key")
 
-    # Canonical Request
     method = req.method
-    canonical_uri = quote(req.path, safe="/-_.~")
+    canonical_uri = _get_canonical_uri(req)
     
-    # Canonical Query String
     query_args = []
     for key, value in req.args.items(multi=True):
         query_args.append((key, value))
@@ -100,7 +115,6 @@ def _verify_sigv4_header(req: Any, auth_header: str) -> Principal | None:
         canonical_query_parts.append(f"{quote(k, safe='-_.~')}={quote(v, safe='-_.~')}")
     canonical_query_string = "&".join(canonical_query_parts)
 
-    # Canonical Headers
     signed_headers_list = signed_headers_str.split(";")
     canonical_headers_parts = []
     for header in signed_headers_list:
@@ -108,22 +122,20 @@ def _verify_sigv4_header(req: Any, auth_header: str) -> Principal | None:
         if header_val is None:
              header_val = ""
         
+        if header.lower() == 'expect' and header_val == "":
+            header_val = "100-continue"
+        
         header_val = " ".join(header_val.split())
         canonical_headers_parts.append(f"{header.lower()}:{header_val}\n")
     canonical_headers = "".join(canonical_headers_parts)
 
-    # Payload Hash
     payload_hash = req.headers.get("X-Amz-Content-Sha256")
     if not payload_hash:
         payload_hash = hashlib.sha256(req.get_data()).hexdigest()
 
     canonical_request = f"{method}\n{canonical_uri}\n{canonical_query_string}\n{canonical_headers}\n{signed_headers_str}\n{payload_hash}"
 
-    # String to Sign
+    amz_date = req.headers.get("X-Amz-Date") or req.headers.get("Date")
-    amz_date = req.headers.get("X-Amz-Date")
-    if not amz_date:
-        amz_date = req.headers.get("Date")
-    
     if not amz_date:
         raise IamError("Missing Date header")
 
@@ -134,13 +146,12 @@ def _verify_sigv4_header(req: Any, auth_header: str) -> Principal | None:
 
     now = datetime.now(timezone.utc)
     time_diff = abs((now - request_time).total_seconds())
-    if time_diff > 900:  # 15 minutes
+    if time_diff > 900:
         raise IamError("Request timestamp too old or too far in the future")
 
     required_headers = {'host', 'x-amz-date'}
     signed_headers_set = set(signed_headers_str.split(';'))
     if not required_headers.issubset(signed_headers_set):
-        # Some clients might sign 'date' instead of 'x-amz-date'
         if 'date' in signed_headers_set:
             required_headers.remove('x-amz-date')
             required_headers.add('date')
@@ -154,6 +165,18 @@ def _verify_sigv4_header(req: Any, auth_header: str) -> Principal | None:
     calculated_signature = hmac.new(signing_key, string_to_sign.encode("utf-8"), hashlib.sha256).hexdigest()
 
     if not hmac.compare_digest(calculated_signature, signature):
+        # Only log detailed signature debug info if DEBUG_SIGV4 is enabled
+        if current_app.config.get("DEBUG_SIGV4"):
+            logger.warning(
+                "SigV4 signature mismatch",
+                extra={
+                    "path": req.path,
+                    "method": method,
+                    "signed_headers": signed_headers_str,
+                    "content_type": req.headers.get("Content-Type"),
+                    "content_length": req.headers.get("Content-Length"),
+                }
+            )
         raise IamError("SignatureDoesNotMatch")
 
     return _iam().get_principal(access_key)
@@ -187,11 +210,9 @@ def _verify_sigv4_query(req: Any) -> Principal | None:
     if not secret_key:
         raise IamError("Invalid access key")
 
-    # Canonical Request
     method = req.method
-    canonical_uri = quote(req.path, safe="/-_.~")
+    canonical_uri = _get_canonical_uri(req)
     
-    # Canonical Query String
     query_args = []
     for key, value in req.args.items(multi=True):
         if key != "X-Amz-Signature":
@@ -203,16 +224,16 @@ def _verify_sigv4_query(req: Any) -> Principal | None:
         canonical_query_parts.append(f"{quote(k, safe='-_.~')}={quote(v, safe='-_.~')}")
     canonical_query_string = "&".join(canonical_query_parts)
     
-    # Canonical Headers
     signed_headers_list = signed_headers_str.split(";")
     canonical_headers_parts = []
     for header in signed_headers_list:
         val = req.headers.get(header, "").strip()
+        if header.lower() == 'expect' and val == "":
+            val = "100-continue"
         val = " ".join(val.split())
         canonical_headers_parts.append(f"{header}:{val}\n")
     canonical_headers = "".join(canonical_headers_parts)
     
-    # Payload Hash
     payload_hash = "UNSIGNED-PAYLOAD"
     
     canonical_request = "\n".join([
@@ -224,7 +245,6 @@ def _verify_sigv4_query(req: Any) -> Principal | None:
         payload_hash
     ])
     
-    # String to Sign
     algorithm = "AWS4-HMAC-SHA256"
     credential_scope = f"{date_stamp}/{region}/{service}/aws4_request"
     hashed_request = hashlib.sha256(canonical_request.encode('utf-8')).hexdigest()
@@ -235,7 +255,6 @@ def _verify_sigv4_query(req: Any) -> Principal | None:
         hashed_request
     ])
     
-    # Signature
     signing_key = _get_signature_key(secret_key, date_stamp, region, service)
     calculated_signature = hmac.new(signing_key, string_to_sign.encode("utf-8"), hashlib.sha256).hexdigest()
     
@@ -493,7 +512,6 @@ def _generate_presigned_url(
     }
     canonical_query = _encode_query_params(query_params)
 
-    # Determine host and scheme from config or request
     api_base = current_app.config.get("API_BASE_URL")
     if api_base:
         parsed = urlparse(api_base)
@@ -545,6 +563,28 @@ def _strip_ns(tag: str | None) -> str:
     return tag.split("}")[-1]
 
 
+def _find_element(parent: Element, name: str) -> Optional[Element]:
+    """Find a child element by name, trying both namespaced and non-namespaced variants.
+
+    This handles XML documents that may or may not include namespace prefixes.
+    """
+    el = parent.find(f"{{*}}{name}")
+    if el is None:
+        el = parent.find(name)
+    return el
+
+
+def _find_element_text(parent: Element, name: str, default: str = "") -> str:
+    """Find a child element and return its text content.
+
+    Returns the default value if element not found or has no text.
+    """
+    el = _find_element(parent, name)
+    if el is None or el.text is None:
+        return default
+    return el.text.strip()
+
+
 def _parse_tagging_document(payload: bytes) -> list[dict[str, str]]:
     try:
         root = fromstring(payload)
@@ -561,17 +601,11 @@ def _parse_tagging_document(payload: bytes) -> list[dict[str, str]]:
     for tag_el in list(tagset):
         if _strip_ns(tag_el.tag) != "Tag":
             continue
-        key_el = tag_el.find("{*}Key")
+        key = _find_element_text(tag_el, "Key")
-        if key_el is None:
-            key_el = tag_el.find("Key")
-        value_el = tag_el.find("{*}Value")
-        if value_el is None:
-            value_el = tag_el.find("Value")
-        key = (key_el.text or "").strip() if key_el is not None else ""
         if not key:
             continue
-        value = value_el.text if value_el is not None else ""
+        value = _find_element_text(tag_el, "Value")
-        tags.append({"Key": key, "Value": value or ""})
+        tags.append({"Key": key, "Value": value})
     return tags
 
 
@@ -853,7 +887,6 @@ def _bucket_versioning_handler(bucket_name: str) -> Response:
         current_app.logger.info("Bucket versioning updated", extra={"bucket": bucket_name, "status": status})
         return Response(status=200)
     
-    # GET
     try:
         enabled = storage.is_versioning_enabled(bucket_name)
     except StorageError as exc:
@@ -889,7 +922,7 @@ def _bucket_tagging_handler(bucket_name: str) -> Response:
             return _error_response("NoSuchBucket", str(exc), 404)
         current_app.logger.info("Bucket tags deleted", extra={"bucket": bucket_name})
         return Response(status=204)
-    # PUT
+
     payload = request.get_data(cache=False) or b""
     try:
         tags = _parse_tagging_document(payload)
@@ -914,7 +947,6 @@ def _object_tagging_handler(bucket_name: str, object_key: str) -> Response:
     if error:
         return error
     
-    # For tagging, we use read permission for GET, write for PUT/DELETE
     action = "read" if request.method == "GET" else "write"
     try:
         _authorize_action(principal, bucket_name, action, object_key=object_key)
@@ -1093,10 +1125,8 @@ def _bucket_location_handler(bucket_name: str) -> Response:
     if not storage.bucket_exists(bucket_name):
         return _error_response("NoSuchBucket", "Bucket does not exist", 404)
     
-    # Return the configured AWS_REGION
     region = current_app.config.get("AWS_REGION", "us-east-1")
     root = Element("LocationConstraint")
-    # AWS returns empty for us-east-1, but we'll be explicit
     root.text = region if region != "us-east-1" else None
     return _xml_response(root)
 
@@ -1116,13 +1146,11 @@ def _bucket_acl_handler(bucket_name: str) -> Response:
         return _error_response("NoSuchBucket", "Bucket does not exist", 404)
     
     if request.method == "PUT":
-        # We don't fully implement ACLs, but we accept the request for compatibility
+        # Accept canned ACL headers for S3 compatibility (not fully implemented)
-        # Check for canned ACL header
         canned_acl = request.headers.get("x-amz-acl", "private")
         current_app.logger.info("Bucket ACL set (canned)", extra={"bucket": bucket_name, "acl": canned_acl})
         return Response(status=200)
     
-    # GET - Return a basic ACL document showing full control for owner
     root = Element("AccessControlPolicy")
     owner = SubElement(root, "Owner")
     SubElement(owner, "ID").text = principal.access_key if principal else "anonymous"
@@ -1170,7 +1198,6 @@ def _bucket_list_versions_handler(bucket_name: str) -> Response:
     if key_marker:
         objects = [obj for obj in objects if obj.key > key_marker]
     
-    # Build XML response
     root = Element("ListVersionsResult", xmlns="http://s3.amazonaws.com/doc/2006-03-01/")
     SubElement(root, "Name").text = bucket_name
     SubElement(root, "Prefix").text = prefix
@@ -1188,10 +1215,9 @@ def _bucket_list_versions_handler(bucket_name: str) -> Response:
             is_truncated = True
             break
         
-        # Current version
         version = SubElement(root, "Version")
         SubElement(version, "Key").text = obj.key
-        SubElement(version, "VersionId").text = "null"  # Current version ID
+        SubElement(version, "VersionId").text = "null"
         SubElement(version, "IsLatest").text = "true"
         SubElement(version, "LastModified").text = obj.last_modified.strftime("%Y-%m-%dT%H:%M:%S.000Z")
         SubElement(version, "ETag").text = f'"{obj.etag}"'
@@ -1205,7 +1231,6 @@ def _bucket_list_versions_handler(bucket_name: str) -> Response:
         version_count += 1
         next_key_marker = obj.key
         
-        # Get historical versions
         try:
             versions = storage.list_object_versions(bucket_name, obj.key)
             for v in versions:
@@ -1289,14 +1314,12 @@ def _render_lifecycle_config(config: list) -> Element:
         rule_el = SubElement(root, "Rule")
         SubElement(rule_el, "ID").text = rule.get("ID", "")
         
-        # Filter
         filter_el = SubElement(rule_el, "Filter")
         if rule.get("Prefix"):
             SubElement(filter_el, "Prefix").text = rule.get("Prefix", "")
         
         SubElement(rule_el, "Status").text = rule.get("Status", "Enabled")
         
-        # Expiration
         if "Expiration" in rule:
             exp = rule["Expiration"]
             exp_el = SubElement(rule_el, "Expiration")
@@ -1307,14 +1330,12 @@ def _render_lifecycle_config(config: list) -> Element:
             if exp.get("ExpiredObjectDeleteMarker"):
                 SubElement(exp_el, "ExpiredObjectDeleteMarker").text = "true"
         
-        # NoncurrentVersionExpiration
         if "NoncurrentVersionExpiration" in rule:
             nve = rule["NoncurrentVersionExpiration"]
             nve_el = SubElement(rule_el, "NoncurrentVersionExpiration")
             if "NoncurrentDays" in nve:
                 SubElement(nve_el, "NoncurrentDays").text = str(nve["NoncurrentDays"])
         
-        # AbortIncompleteMultipartUpload
         if "AbortIncompleteMultipartUpload" in rule:
             aimu = rule["AbortIncompleteMultipartUpload"]
             aimu_el = SubElement(rule_el, "AbortIncompleteMultipartUpload")
@@ -1338,29 +1359,24 @@ def _parse_lifecycle_config(payload: bytes) -> list:
     for rule_el in root.findall("{*}Rule") or root.findall("Rule"):
         rule: dict = {}
         
-        # ID
         id_el = rule_el.find("{*}ID") or rule_el.find("ID")
         if id_el is not None and id_el.text:
             rule["ID"] = id_el.text.strip()
         
-        # Filter/Prefix
         filter_el = rule_el.find("{*}Filter") or rule_el.find("Filter")
         if filter_el is not None:
             prefix_el = filter_el.find("{*}Prefix") or filter_el.find("Prefix")
             if prefix_el is not None and prefix_el.text:
                 rule["Prefix"] = prefix_el.text
         
-        # Legacy Prefix (outside Filter)
         if "Prefix" not in rule:
             prefix_el = rule_el.find("{*}Prefix") or rule_el.find("Prefix")
             if prefix_el is not None:
                 rule["Prefix"] = prefix_el.text or ""
         
-        # Status
         status_el = rule_el.find("{*}Status") or rule_el.find("Status")
         rule["Status"] = (status_el.text or "Enabled").strip() if status_el is not None else "Enabled"
         
-        # Expiration
         exp_el = rule_el.find("{*}Expiration") or rule_el.find("Expiration")
         if exp_el is not None:
             expiration: dict = {}
@@ -1376,7 +1392,6 @@ def _parse_lifecycle_config(payload: bytes) -> list:
             if expiration:
                 rule["Expiration"] = expiration
         
-        # NoncurrentVersionExpiration
         nve_el = rule_el.find("{*}NoncurrentVersionExpiration") or rule_el.find("NoncurrentVersionExpiration")
         if nve_el is not None:
             nve: dict = {}
@@ -1386,7 +1401,6 @@ def _parse_lifecycle_config(payload: bytes) -> list:
             if nve:
                 rule["NoncurrentVersionExpiration"] = nve
         
-        # AbortIncompleteMultipartUpload
         aimu_el = rule_el.find("{*}AbortIncompleteMultipartUpload") or rule_el.find("AbortIncompleteMultipartUpload")
         if aimu_el is not None:
             aimu: dict = {}
@@ -1424,7 +1438,6 @@ def _bucket_quota_handler(bucket_name: str) -> Response:
         if not quota:
             return _error_response("NoSuchQuotaConfiguration", "No quota configuration found", 404)
         
-        # Return as JSON for simplicity (not a standard S3 API)
         stats = storage.bucket_stats(bucket_name)
         return jsonify({
             "quota": quota,
@@ -1436,7 +1449,7 @@ def _bucket_quota_handler(bucket_name: str) -> Response:
     
     if request.method == "DELETE":
         try:
-            storage.set_bucket_quota(bucket_name, max_size_bytes=None, max_objects=None)
+            storage.set_bucket_quota(bucket_name, max_bytes=None, max_objects=None)
         except StorageError as exc:
             return _error_response("NoSuchBucket", str(exc), 404)
         current_app.logger.info("Bucket quota deleted", extra={"bucket": bucket_name})
@@ -1453,7 +1466,6 @@ def _bucket_quota_handler(bucket_name: str) -> Response:
     if max_size_bytes is None and max_objects is None:
         return _error_response("InvalidArgument", "At least one of max_size_bytes or max_objects is required", 400)
     
-    # Validate types
     if max_size_bytes is not None:
         try:
             max_size_bytes = int(max_size_bytes)
@@ -1471,7 +1483,7 @@ def _bucket_quota_handler(bucket_name: str) -> Response:
             return _error_response("InvalidArgument", f"max_objects {exc}", 400)
     
     try:
-        storage.set_bucket_quota(bucket_name, max_size_bytes=max_size_bytes, max_objects=max_objects)
+        storage.set_bucket_quota(bucket_name, max_bytes=max_size_bytes, max_objects=max_objects)
     except StorageError as exc:
         return _error_response("NoSuchBucket", str(exc), 404)
     
@@ -1564,7 +1576,6 @@ def _bulk_delete_handler(bucket_name: str) -> Response:
     return _xml_response(result, status=200)
 
 
-# ---------------------- routes ----------------------
 @s3_api_bp.get("/")
 @limiter.limit("60 per minute")
 def list_buckets() -> Response:
@@ -1642,7 +1653,6 @@ def bucket_handler(bucket_name: str) -> Response:
         current_app.logger.info("Bucket deleted", extra={"bucket": bucket_name})
         return Response(status=204)
 
-    # GET - list objects (supports both ListObjects and ListObjectsV2)
     principal, error = _require_principal()
     try:
         _authorize_action(principal, bucket_name, "list")
@@ -1650,18 +1660,12 @@ def bucket_handler(bucket_name: str) -> Response:
         if error:
             return error
         return _error_response("AccessDenied", str(exc), 403)
-    try:
-        objects = storage.list_objects_all(bucket_name)
-    except StorageError as exc:
-        return _error_response("NoSuchBucket", str(exc), 404)
 
-    # Check if this is ListObjectsV2 (list-type=2)
     list_type = request.args.get("list-type")
     prefix = request.args.get("prefix", "")
     delimiter = request.args.get("delimiter", "")
     max_keys = min(int(request.args.get("max-keys", current_app.config["UI_PAGE_SIZE"])), 1000)
     
-    # Pagination markers
     marker = request.args.get("marker", "")  # ListObjects v1
     continuation_token = request.args.get("continuation-token", "")  # ListObjectsV2
     start_after = request.args.get("start-after", "")  # ListObjectsV2
@@ -1671,7 +1675,6 @@ def bucket_handler(bucket_name: str) -> Response:
     effective_start = ""
     if list_type == "2":
         if continuation_token:
-            import base64
             try:
                 effective_start = base64.urlsafe_b64decode(continuation_token.encode()).decode("utf-8")
             except Exception:
@@ -1681,11 +1684,17 @@ def bucket_handler(bucket_name: str) -> Response:
     else:
         effective_start = marker
     
-    if prefix:
+    fetch_keys = max_keys * 10 if delimiter else max_keys
-        objects = [obj for obj in objects if obj.key.startswith(prefix)]
+    try:
-    
+        list_result = storage.list_objects(
-    if effective_start:
+            bucket_name,
-        objects = [obj for obj in objects if obj.key > effective_start]
+            max_keys=fetch_keys,
+            continuation_token=effective_start or None,
+            prefix=prefix or None,
+        )
+        objects = list_result.objects
+    except StorageError as exc:
+        return _error_response("NoSuchBucket", str(exc), 404)
     
     common_prefixes: list[str] = []
     filtered_objects: list = []
@@ -1694,7 +1703,6 @@ def bucket_handler(bucket_name: str) -> Response:
         for obj in objects:
             key_after_prefix = obj.key[len(prefix):] if prefix else obj.key
             if delimiter in key_after_prefix:
-                # This is a "folder" - extract the common prefix
                 common_prefix = prefix + key_after_prefix.split(delimiter)[0] + delimiter
                 if common_prefix not in seen_prefixes:
                     seen_prefixes.add(common_prefix)
@@ -1705,7 +1713,7 @@ def bucket_handler(bucket_name: str) -> Response:
         common_prefixes = sorted(common_prefixes)
     
     total_items = len(objects) + len(common_prefixes)
-    is_truncated = total_items > max_keys
+    is_truncated = total_items > max_keys or list_result.is_truncated
     
     if len(objects) >= max_keys:
         objects = objects[:max_keys]
@@ -1723,7 +1731,6 @@ def bucket_handler(bucket_name: str) -> Response:
             next_marker = common_prefixes[-1].rstrip(delimiter) if delimiter else common_prefixes[-1]
         
         if list_type == "2" and next_marker:
-            import base64
             next_continuation_token = base64.urlsafe_b64encode(next_marker.encode()).decode("utf-8")
 
     if list_type == "2":
@@ -1792,7 +1799,6 @@ def object_handler(bucket_name: str, object_key: str):
     if "tagging" in request.args:
         return _object_tagging_handler(bucket_name, object_key)
 
-    # Multipart Uploads
     if request.method == "POST":
         if "uploads" in request.args:
             return _initiate_multipart_upload(bucket_name, object_key)
@@ -1845,9 +1851,7 @@ def object_handler(bucket_name: str, object_key: str):
         response = Response(status=200)
         response.headers["ETag"] = f'"{meta.etag}"'
         
-        # Trigger replication if not a replication request
+        if "S3ReplicationAgent" not in request.headers.get("User-Agent", ""):
-        user_agent = request.headers.get("User-Agent", "")
-        if "S3ReplicationAgent" not in user_agent:
             _replication_manager().trigger_replication(bucket_name, object_key, action="write")
             
         return response
@@ -1866,31 +1870,25 @@ def object_handler(bucket_name: str, object_key: str):
         metadata = storage.get_object_metadata(bucket_name, object_key)
         mimetype = mimetypes.guess_type(object_key)[0] or "application/octet-stream"
         
-        # Check if object is encrypted and needs decryption
         is_encrypted = "x-amz-server-side-encryption" in metadata
         
         if request.method == "GET":
             if is_encrypted and hasattr(storage, 'get_object_data'):
-                # Use encrypted storage to decrypt
                 try:
                     data, clean_metadata = storage.get_object_data(bucket_name, object_key)
                     response = Response(data, mimetype=mimetype)
                     logged_bytes = len(data)
-                    # Use decrypted size for Content-Length
                     response.headers["Content-Length"] = len(data)
                     etag = hashlib.md5(data).hexdigest()
                 except StorageError as exc:
                     return _error_response("InternalError", str(exc), 500)
             else:
-                # Stream unencrypted file directly
                 stat = path.stat()
                 response = Response(_stream_file(path), mimetype=mimetype, direct_passthrough=True)
                 logged_bytes = stat.st_size
                 etag = storage._compute_etag(path)
         else:
-            # HEAD request
             if is_encrypted and hasattr(storage, 'get_object_data'):
-                # For encrypted objects, we need to report decrypted size
                 try:
                     data, _ = storage.get_object_data(bucket_name, object_key)
                     response = Response(status=200)
@@ -1919,7 +1917,6 @@ def object_handler(bucket_name: str, object_key: str):
     storage.delete_object(bucket_name, object_key)
     current_app.logger.info("Object deleted", extra={"bucket": bucket_name, "key": object_key})
     
-    # Trigger replication if not a replication request
     user_agent = request.headers.get("User-Agent", "")
     if "S3ReplicationAgent" not in user_agent:
         _replication_manager().trigger_replication(bucket_name, object_key, action="delete")
@@ -2200,7 +2197,6 @@ class AwsChunkedDecoder:
                 self.chunk_remaining -= len(chunk)
                 
                 if self.chunk_remaining == 0:
-                    # Read CRLF after chunk data
                     crlf = self.stream.read(2)
                     if crlf != b"\r\n":
                         raise IOError("Malformed chunk: missing CRLF")
@@ -2219,7 +2215,6 @@ class AwsChunkedDecoder:
                 
                 try:
                     line_str = line.decode("ascii").strip()
-                    # Handle chunk-signature extension if present (e.g. "1000;chunk-signature=...")
                     if ";" in line_str:
                         line_str = line_str.split(";")[0]
                     chunk_size = int(line_str, 16)
@@ -2375,7 +2370,6 @@ def _abort_multipart_upload(bucket_name: str, object_key: str) -> Response:
     try:
         _storage().abort_multipart_upload(bucket_name, upload_id)
     except StorageError as exc:
-        # Abort is idempotent, but if bucket missing...
         if "Bucket does not exist" in str(exc):
             return _error_response("NoSuchBucket", str(exc), 404)
             
@@ -2385,7 +2379,6 @@ def _abort_multipart_upload(bucket_name: str, object_key: str) -> Response:
 @s3_api_bp.before_request
 def resolve_principal():
     g.principal = None
-    # Try SigV4
     try:
         if ("Authorization" in request.headers and request.headers["Authorization"].startswith("AWS4-HMAC-SHA256")) or \
            (request.args.get("X-Amz-Algorithm") == "AWS4-HMAC-SHA256"):
@@ -2394,7 +2387,6 @@ def resolve_principal():
     except Exception:
         pass
     
-    # Try simple auth headers (internal/testing)
     access_key = request.headers.get("X-Access-Key")
     secret_key = request.headers.get("X-Secret-Key")
     if access_key and secret_key:

app/storage.py

@@ -7,9 +7,11 @@ import os
 import re
 import shutil
 import stat
+import threading
 import time
 import unicodedata
 import uuid
+from collections import OrderedDict
 from contextlib import contextmanager
 from dataclasses import dataclass
 from datetime import datetime, timezone
@@ -128,11 +130,18 @@ class ObjectStorage:
     BUCKET_VERSIONS_DIR = "versions"
     MULTIPART_MANIFEST = "manifest.json"
     BUCKET_CONFIG_FILE = ".bucket.json"
+    KEY_INDEX_CACHE_TTL = 30
+    OBJECT_CACHE_MAX_SIZE = 100  # Maximum number of buckets to cache
 
     def __init__(self, root: Path) -> None:
         self.root = Path(root)
         self.root.mkdir(parents=True, exist_ok=True)
         self._ensure_system_roots()
+        # LRU cache for object metadata with thread-safe access
+        self._object_cache: OrderedDict[str, tuple[Dict[str, ObjectMeta], float]] = OrderedDict()
+        self._cache_lock = threading.Lock()
+        # Cache version counter for detecting stale reads
+        self._cache_version: Dict[str, int] = {}
 
     def list_buckets(self) -> List[BucketMeta]:
         buckets: List[BucketMeta] = []
@@ -142,7 +151,7 @@ class ObjectStorage:
                 buckets.append(
                     BucketMeta(
                         name=bucket.name,
-                        created_at=datetime.fromtimestamp(stat.st_ctime),
+                        created_at=datetime.fromtimestamp(stat.st_ctime, timezone.utc),
                     )
                 )
         return buckets
@@ -190,7 +199,6 @@ class ObjectStorage:
         version_count = 0
         version_bytes = 0
 
-        # Count current objects in the bucket folder
         for path in bucket_path.rglob("*"):
             if path.is_file():
                 rel = path.relative_to(bucket_path)
@@ -202,7 +210,6 @@ class ObjectStorage:
                     object_count += 1
                     total_bytes += stat.st_size
 
-        # Count archived versions in the system folder
         versions_root = self._bucket_versions_root(bucket_name)
         if versions_root.exists():
             for path in versions_root.rglob("*.bin"):
@@ -216,8 +223,8 @@ class ObjectStorage:
             "bytes": total_bytes,
             "version_count": version_count,
             "version_bytes": version_bytes,
-            "total_objects": object_count + version_count,  # All objects including versions
+            "total_objects": object_count + version_count,
-            "total_bytes": total_bytes + version_bytes,  # All storage including versions
+            "total_bytes": total_bytes + version_bytes, 
         }
         
         try:
@@ -274,32 +281,20 @@ class ObjectStorage:
             raise StorageError("Bucket does not exist")
         bucket_id = bucket_path.name
 
-        # Collect all matching object keys first (lightweight - just paths)
+        object_cache = self._get_object_cache(bucket_id, bucket_path)
-        all_keys: List[str] = []
+        
-        for path in bucket_path.rglob("*"):
+        all_keys = sorted(object_cache.keys())
-            if path.is_file():
+        
-                rel = path.relative_to(bucket_path)
+        if prefix:
-                if rel.parts and rel.parts[0] in self.INTERNAL_FOLDERS:
+            all_keys = [k for k in all_keys if k.startswith(prefix)]
-                    continue
-                key = str(rel.as_posix())
-                if prefix and not key.startswith(prefix):
-                    continue
-                all_keys.append(key)
         
-        all_keys.sort()
         total_count = len(all_keys)
-        
-        # Handle continuation token (the key to start after)
         start_index = 0
         if continuation_token:
             try:
-                # continuation_token is the last key from previous page
+                import bisect
-                for i, key in enumerate(all_keys):
+                start_index = bisect.bisect_right(all_keys, continuation_token)
-                    if key > continuation_token:
+                if start_index >= total_count:
-                        start_index = i
-                        break
-                else:
-                    # Token is past all keys
                     return ListObjectsResult(
                         objects=[],
                         is_truncated=False,
@@ -307,34 +302,17 @@ class ObjectStorage:
                         total_count=total_count,
                     )
             except Exception:
-                pass  # Invalid token, start from beginning
+                pass  
         
-        # Get the slice we need
         end_index = start_index + max_keys
         keys_slice = all_keys[start_index:end_index]
         is_truncated = end_index < total_count
 
-        # Now load full metadata only for the objects we're returning
         objects: List[ObjectMeta] = []
         for key in keys_slice:
-            safe_key = self._sanitize_object_key(key)
+            obj = object_cache.get(key)
-            path = bucket_path / safe_key
+            if obj:
-            if not path.exists():
+                objects.append(obj)
-                continue  # Object may have been deleted
-            try:
-                stat = path.stat()
-                metadata = self._read_metadata(bucket_id, safe_key)
-                objects.append(
-                    ObjectMeta(
-                        key=key,
-                        size=stat.st_size,
-                        last_modified=datetime.fromtimestamp(stat.st_mtime),
-                        etag=self._compute_etag(path),
-                        metadata=metadata or None,
-                    )
-                )
-            except OSError:
-                continue  # File may have been deleted during iteration
         
         next_token = keys_slice[-1] if is_truncated and keys_slice else None
         
@@ -368,14 +346,12 @@ class ObjectStorage:
         destination = bucket_path / safe_key
         destination.parent.mkdir(parents=True, exist_ok=True)
 
-        # Check if this is an overwrite (won't add to object count)
         is_overwrite = destination.exists()
         existing_size = destination.stat().st_size if is_overwrite else 0
 
         if self._is_versioning_enabled(bucket_path) and is_overwrite:
             self._archive_current_version(bucket_id, safe_key, reason="overwrite")
 
-        # Write to temp file first to get actual size
         tmp_dir = self._system_root_path() / self.SYSTEM_TMP_DIR
         tmp_dir.mkdir(parents=True, exist_ok=True)
         tmp_path = tmp_dir / f"{uuid.uuid4().hex}.tmp"
@@ -387,9 +363,7 @@ class ObjectStorage:
             
             new_size = tmp_path.stat().st_size
             
-            # Check quota before finalizing
             if enforce_quota:
-                # Calculate net change (new size minus size being replaced)
                 size_delta = new_size - existing_size
                 object_delta = 0 if is_overwrite else 1
                 
@@ -405,29 +379,29 @@ class ObjectStorage:
                         quota_check["usage"],
                     )
             
-            # Move to final destination
             shutil.move(str(tmp_path), str(destination))
             
         finally:
-            # Clean up temp file if it still exists
             try:
                 tmp_path.unlink(missing_ok=True)
             except OSError:
                 pass
 
         stat = destination.stat()
-        if metadata:
+        etag = checksum.hexdigest()
-            self._write_metadata(bucket_id, safe_key, metadata)
+        
-        else:
+        internal_meta = {"__etag__": etag, "__size__": str(stat.st_size)}
-            self._delete_metadata(bucket_id, safe_key)
+        combined_meta = {**internal_meta, **(metadata or {})}
+        self._write_metadata(bucket_id, safe_key, combined_meta)
         
         self._invalidate_bucket_stats_cache(bucket_id)
+        self._invalidate_object_cache(bucket_id)
         
         return ObjectMeta(
             key=safe_key.as_posix(),
             size=stat.st_size,
-            last_modified=datetime.fromtimestamp(stat.st_mtime),
+            last_modified=datetime.fromtimestamp(stat.st_mtime, timezone.utc),
-            etag=checksum.hexdigest(),
+            etag=etag,
             metadata=metadata,
         )
 
@@ -453,16 +427,14 @@ class ObjectStorage:
         for parent in path.parents:
             if parent == stop_at:
                 break
-            # Retry a few times with small delays for Windows/OneDrive
             for attempt in range(3):
                 try:
                     if parent.exists() and not any(parent.iterdir()):
                         parent.rmdir()
-                        break  # Success, move to next parent
+                        break 
                 except OSError:
                     if attempt < 2:
-                        time.sleep(0.1)  # Brief delay before retry
+                        time.sleep(0.1)
-                    # Final attempt failed - continue to next parent
                     break
 
     def delete_object(self, bucket_name: str, object_key: str) -> None:
@@ -479,6 +451,7 @@ class ObjectStorage:
         self._delete_metadata(bucket_id, rel)
         
         self._invalidate_bucket_stats_cache(bucket_id)
+        self._invalidate_object_cache(bucket_id)
         self._cleanup_empty_parents(path, bucket_path)
 
     def purge_object(self, bucket_name: str, object_key: str) -> None:
@@ -499,8 +472,8 @@ class ObjectStorage:
         if legacy_version_dir.exists():
             shutil.rmtree(legacy_version_dir, ignore_errors=True)
         
-        # Invalidate bucket stats cache
         self._invalidate_bucket_stats_cache(bucket_id)
+        self._invalidate_object_cache(bucket_id)
         self._cleanup_empty_parents(target, bucket_path)
 
     def is_versioning_enabled(self, bucket_name: str) -> bool:
@@ -612,7 +585,6 @@ class ObjectStorage:
         bucket_path = self._require_bucket_path(bucket_name)
         
         if max_bytes is None and max_objects is None:
-            # Remove quota entirely
             self._set_bucket_config_entry(bucket_path.name, "quota", None)
             return
         
@@ -654,9 +626,7 @@ class ObjectStorage:
                 "message": None,
             }
         
-        # Get current stats (uses cache when available)
         stats = self.bucket_stats(bucket_name)
-        # Use totals which include versions for quota enforcement
         current_bytes = stats.get("total_bytes", stats.get("bytes", 0))
         current_objects = stats.get("total_objects", stats.get("objects", 0))
         
@@ -766,8 +736,6 @@ class ObjectStorage:
         bucket_id = bucket_path.name
         safe_key = self._sanitize_object_key(object_key)
         version_dir = self._version_dir(bucket_id, safe_key)
-        if not version_dir.exists():
-            version_dir = self._legacy_version_dir(bucket_id, safe_key)
         if not version_dir.exists():
             version_dir = self._legacy_version_dir(bucket_id, safe_key)
             if not version_dir.exists():
@@ -817,7 +785,7 @@ class ObjectStorage:
         return ObjectMeta(
             key=safe_key.as_posix(),
             size=stat.st_size,
-            last_modified=datetime.fromtimestamp(stat.st_mtime),
+            last_modified=datetime.fromtimestamp(stat.st_mtime, timezone.utc),
             etag=self._compute_etag(destination),
             metadata=metadata or None,
         )
@@ -916,44 +884,72 @@ class ObjectStorage:
         part_number: int,
         stream: BinaryIO,
     ) -> str:
+        """Upload a part for a multipart upload.
+
+        Uses file locking to safely update the manifest and handle concurrent uploads.
+        """
         if part_number < 1:
             raise StorageError("part_number must be >= 1")
         bucket_path = self._bucket_path(bucket_name)
 
-        # Get the upload root directory
         upload_root = self._multipart_dir(bucket_path.name, upload_id)
         if not upload_root.exists():
             upload_root = self._legacy_multipart_dir(bucket_path.name, upload_id)
         if not upload_root.exists():
             raise StorageError("Multipart upload not found")
 
-        # Write the part data first (can happen concurrently)
+        # Write part to temporary file first, then rename atomically
         checksum = hashlib.md5()
         part_filename = f"part-{part_number:05d}.part"
         part_path = upload_root / part_filename
-        with part_path.open("wb") as target:
+        temp_path = upload_root / f".{part_filename}.tmp"
+
+        try:
+            with temp_path.open("wb") as target:
                 shutil.copyfileobj(_HashingReader(stream, checksum), target)
+
+            # Atomic rename (or replace on Windows)
+            temp_path.replace(part_path)
+        except OSError:
+            # Clean up temp file on failure
+            try:
+                temp_path.unlink(missing_ok=True)
+            except OSError:
+                pass
+            raise
+
         record = {
             "etag": checksum.hexdigest(),
             "size": part_path.stat().st_size,
             "filename": part_filename,
         }
 
-        # Update manifest with file locking to prevent race conditions
         manifest_path = upload_root / self.MULTIPART_MANIFEST
         lock_path = upload_root / ".manifest.lock"
 
+        # Retry loop for handling transient lock/read failures
+        max_retries = 3
+        for attempt in range(max_retries):
+            try:
                 with lock_path.open("w") as lock_file:
                     with _file_lock(lock_file):
-                # Re-read manifest under lock to get latest state
                         try:
                             manifest = json.loads(manifest_path.read_text(encoding="utf-8"))
                         except (OSError, json.JSONDecodeError) as exc:
+                            if attempt < max_retries - 1:
+                                time.sleep(0.1 * (attempt + 1))
+                                continue
                             raise StorageError("Multipart manifest unreadable") from exc
 
                         parts = manifest.setdefault("parts", {})
                         parts[str(part_number)] = record
                         manifest_path.write_text(json.dumps(manifest), encoding="utf-8")
+                break
+            except OSError as exc:
+                if attempt < max_retries - 1:
+                    time.sleep(0.1 * (attempt + 1))
+                    continue
+                raise StorageError(f"Failed to update multipart manifest: {exc}") from exc
 
         return record["etag"]
 
@@ -999,11 +995,9 @@ class ObjectStorage:
         safe_key = self._sanitize_object_key(manifest["object_key"])
         destination = bucket_path / safe_key
         
-        # Check if this is an overwrite
         is_overwrite = destination.exists()
         existing_size = destination.stat().st_size if is_overwrite else 0
         
-        # Check quota before writing
         if enforce_quota:
             size_delta = total_size - existing_size
             object_delta = 0 if is_overwrite else 1
@@ -1060,12 +1054,13 @@ class ObjectStorage:
         shutil.rmtree(upload_root, ignore_errors=True)
 
         self._invalidate_bucket_stats_cache(bucket_id)
+        self._invalidate_object_cache(bucket_id)
 
         stat = destination.stat()
         return ObjectMeta(
             key=safe_key.as_posix(),
             size=stat.st_size,
-            last_modified=datetime.fromtimestamp(stat.st_mtime),
+            last_modified=datetime.fromtimestamp(stat.st_mtime, timezone.utc),
             etag=checksum.hexdigest(),
             metadata=metadata,
         )
@@ -1163,6 +1158,202 @@ class ObjectStorage:
     def _legacy_multipart_dir(self, bucket_name: str, upload_id: str) -> Path:
         return self._legacy_multipart_bucket_root(bucket_name) / upload_id
 
+    def _fast_list_keys(self, bucket_path: Path) -> List[str]:
+        """Fast directory walk using os.scandir instead of pathlib.rglob.
+        
+        This is significantly faster for large directories (10K+ files).
+        Returns just the keys (for backward compatibility).
+        """
+        return list(self._build_object_cache(bucket_path).keys())
+
+    def _build_object_cache(self, bucket_path: Path) -> Dict[str, ObjectMeta]:
+        """Build a complete object metadata cache for a bucket.
+        
+        Uses os.scandir for fast directory walking and a persistent etag index.
+        """
+        from concurrent.futures import ThreadPoolExecutor
+        
+        bucket_id = bucket_path.name
+        objects: Dict[str, ObjectMeta] = {}
+        bucket_str = str(bucket_path)
+        bucket_len = len(bucket_str) + 1
+        
+        etag_index_path = self._system_bucket_root(bucket_id) / "etag_index.json"
+        meta_cache: Dict[str, str] = {}
+        index_mtime: float = 0
+        
+        if etag_index_path.exists():
+            try:
+                index_mtime = etag_index_path.stat().st_mtime
+                with open(etag_index_path, 'r', encoding='utf-8') as f:
+                    meta_cache = json.load(f)
+            except (OSError, json.JSONDecodeError):
+                meta_cache = {}
+        
+        meta_root = self._bucket_meta_root(bucket_id)
+        needs_rebuild = False
+        
+        if meta_root.exists() and index_mtime > 0:
+            def check_newer(dir_path: str) -> bool:
+                try:
+                    with os.scandir(dir_path) as it:
+                        for entry in it:
+                            if entry.is_dir(follow_symlinks=False):
+                                if check_newer(entry.path):
+                                    return True
+                            elif entry.is_file(follow_symlinks=False) and entry.name.endswith('.meta.json'):
+                                if entry.stat().st_mtime > index_mtime:
+                                    return True
+                except OSError:
+                    pass
+                return False
+            needs_rebuild = check_newer(str(meta_root))
+        elif not meta_cache:
+            needs_rebuild = True
+            
+        if needs_rebuild and meta_root.exists():
+            meta_str = str(meta_root)
+            meta_len = len(meta_str) + 1
+            meta_files: list[tuple[str, str]] = []
+            
+            def collect_meta_files(dir_path: str) -> None:
+                try:
+                    with os.scandir(dir_path) as it:
+                        for entry in it:
+                            if entry.is_dir(follow_symlinks=False):
+                                collect_meta_files(entry.path)
+                            elif entry.is_file(follow_symlinks=False) and entry.name.endswith('.meta.json'):
+                                rel = entry.path[meta_len:]
+                                key = rel[:-10].replace(os.sep, '/')
+                                meta_files.append((key, entry.path))
+                except OSError:
+                    pass
+            
+            collect_meta_files(meta_str)
+            
+            def read_meta_file(item: tuple[str, str]) -> tuple[str, str | None]:
+                key, path = item
+                try:
+                    with open(path, 'rb') as f:
+                        content = f.read()
+                    etag_marker = b'"__etag__"'
+                    idx = content.find(etag_marker)
+                    if idx != -1:
+                        start = content.find(b'"', idx + len(etag_marker) + 1)
+                        if start != -1:
+                            end = content.find(b'"', start + 1)
+                            if end != -1:
+                                return key, content[start+1:end].decode('utf-8')
+                    return key, None
+                except (OSError, UnicodeDecodeError):
+                    return key, None
+            
+            if meta_files:
+                meta_cache = {}
+                with ThreadPoolExecutor(max_workers=min(64, len(meta_files))) as executor:
+                    for key, etag in executor.map(read_meta_file, meta_files):
+                        if etag:
+                            meta_cache[key] = etag
+                
+                try:
+                    etag_index_path.parent.mkdir(parents=True, exist_ok=True)
+                    with open(etag_index_path, 'w', encoding='utf-8') as f:
+                        json.dump(meta_cache, f)
+                except OSError:
+                    pass
+        
+        def scan_dir(dir_path: str) -> None:
+            try:
+                with os.scandir(dir_path) as it:
+                    for entry in it:
+                        if entry.is_dir(follow_symlinks=False):
+                            rel_start = entry.path[bucket_len:].split(os.sep)[0] if len(entry.path) > bucket_len else entry.name
+                            if rel_start in self.INTERNAL_FOLDERS:
+                                continue
+                            scan_dir(entry.path)
+                        elif entry.is_file(follow_symlinks=False):
+                            rel = entry.path[bucket_len:]
+                            first_part = rel.split(os.sep)[0] if os.sep in rel else rel
+                            if first_part in self.INTERNAL_FOLDERS:
+                                continue
+                            
+                            key = rel.replace(os.sep, '/')
+                            try:
+                                stat = entry.stat()
+                                
+                                etag = meta_cache.get(key)
+                                
+                                if not etag:
+                                    etag = f'"{stat.st_size}-{int(stat.st_mtime)}"'
+                                
+                                objects[key] = ObjectMeta(
+                                    key=key,
+                                    size=stat.st_size,
+                                    last_modified=datetime.fromtimestamp(stat.st_mtime, timezone.utc),
+                                    etag=etag,
+                                    metadata=None, 
+                                )
+                            except OSError:
+                                pass
+            except OSError:
+                pass
+        
+        scan_dir(bucket_str)
+        return objects
+
+    def _get_object_cache(self, bucket_id: str, bucket_path: Path) -> Dict[str, ObjectMeta]:
+        """Get cached object metadata for a bucket, refreshing if stale.
+
+        Uses LRU eviction to prevent unbounded cache growth.
+        Thread-safe with version tracking to detect concurrent invalidations.
+        """
+        now = time.time()
+
+        with self._cache_lock:
+            cached = self._object_cache.get(bucket_id)
+            cache_version = self._cache_version.get(bucket_id, 0)
+
+            if cached:
+                objects, timestamp = cached
+                if now - timestamp < self.KEY_INDEX_CACHE_TTL:
+                    # Move to end (most recently used)
+                    self._object_cache.move_to_end(bucket_id)
+                    return objects
+
+        # Build cache outside lock to avoid holding lock during I/O
+        objects = self._build_object_cache(bucket_path)
+
+        with self._cache_lock:
+            # Check if cache was invalidated while we were building
+            current_version = self._cache_version.get(bucket_id, 0)
+            if current_version != cache_version:
+                # Cache was invalidated, rebuild
+                objects = self._build_object_cache(bucket_path)
+
+            # Evict oldest entries if cache is full
+            while len(self._object_cache) >= self.OBJECT_CACHE_MAX_SIZE:
+                self._object_cache.popitem(last=False)
+
+            self._object_cache[bucket_id] = (objects, time.time())
+            self._object_cache.move_to_end(bucket_id)
+
+        return objects
+
+    def _invalidate_object_cache(self, bucket_id: str) -> None:
+        """Invalidate the object cache and etag index for a bucket.
+
+        Increments version counter to signal stale reads.
+        """
+        with self._cache_lock:
+            self._object_cache.pop(bucket_id, None)
+            self._cache_version[bucket_id] = self._cache_version.get(bucket_id, 0) + 1
+
+        etag_index_path = self._system_bucket_root(bucket_id) / "etag_index.json"
+        try:
+            etag_index_path.unlink(missing_ok=True)
+        except OSError:
+            pass
+
     def _ensure_system_roots(self) -> None:
         for path in (
             self._system_root_path(),

app/ui.py

@@ -189,7 +189,7 @@ def inject_nav_state() -> dict[str, Any]:
     return {
         "principal": principal,
         "can_manage_iam": can_manage,
-        "can_view_metrics": can_manage,  # Only admins can view metrics
+        "can_view_metrics": can_manage, 
         "csrf_token": generate_csrf,
     }
 
@@ -294,7 +294,6 @@ def bucket_detail(bucket_name: str):
     storage = _storage()
     try:
         _authorize_ui(principal, bucket_name, "list")
-        # Don't load objects here - UI fetches them asynchronously via /buckets/<name>/objects
         if not storage.bucket_exists(bucket_name):
             raise StorageError("Bucket does not exist")
     except (StorageError, IamError) as exc:
@@ -343,7 +342,6 @@ def bucket_detail(bucket_name: str):
         except IamError:
             can_manage_versioning = False
 
-    # Check replication permission
     can_manage_replication = False
     if principal:
         try:
@@ -352,7 +350,6 @@ def bucket_detail(bucket_name: str):
         except IamError:
             can_manage_replication = False
 
-    # Check if user is admin (can configure replication settings, not just toggle)
     is_replication_admin = False
     if principal:
         try:
@@ -361,12 +358,9 @@ def bucket_detail(bucket_name: str):
         except IamError:
             is_replication_admin = False
 
-    # Replication info - don't compute sync status here (it's slow), let JS fetch it async
     replication_rule = _replication().get_rule(bucket_name)
-    # Load connections for admin, or for non-admin if there's an existing rule (to show target name)
     connections = _connections().list() if (is_replication_admin or replication_rule) else []
 
-    # Encryption settings
     encryption_config = storage.get_bucket_encryption(bucket_name)
     kms_manager = _kms()
     kms_keys = kms_manager.list_keys() if kms_manager else []
@@ -374,7 +368,6 @@ def bucket_detail(bucket_name: str):
     encryption_enabled = current_app.config.get("ENCRYPTION_ENABLED", False)
     can_manage_encryption = can_manage_versioning  # Same as other bucket properties
 
-    # Quota settings (admin only)
     bucket_quota = storage.get_bucket_quota(bucket_name)
     bucket_stats = storage.bucket_stats(bucket_name)
     can_manage_quota = False
@@ -384,7 +377,6 @@ def bucket_detail(bucket_name: str):
     except IamError:
         pass
 
-    # Pass the objects API endpoint URL for async loading
     objects_api_url = url_for("ui.list_bucket_objects", bucket_name=bucket_name)
 
     return render_template(
@@ -423,7 +415,7 @@ def list_bucket_objects(bucket_name: str):
     except IamError as exc:
         return jsonify({"error": str(exc)}), 403
 
-    max_keys = min(int(request.args.get("max_keys", 100)), 1000)
+    max_keys = min(int(request.args.get("max_keys", 1000)), 100000)
     continuation_token = request.args.get("continuation_token") or None
     prefix = request.args.get("prefix") or None
 
@@ -442,6 +434,14 @@ def list_bucket_objects(bucket_name: str):
     except StorageError:
         versioning_enabled = False
 
+    # Pre-compute URL templates once (not per-object) for performance
+    # Frontend will construct actual URLs by replacing KEY_PLACEHOLDER
+    preview_template = url_for("ui.object_preview", bucket_name=bucket_name, object_key="KEY_PLACEHOLDER")
+    delete_template = url_for("ui.delete_object", bucket_name=bucket_name, object_key="KEY_PLACEHOLDER")
+    presign_template = url_for("ui.object_presign", bucket_name=bucket_name, object_key="KEY_PLACEHOLDER")
+    versions_template = url_for("ui.object_versions", bucket_name=bucket_name, object_key="KEY_PLACEHOLDER")
+    restore_template = url_for("ui.restore_object_version", bucket_name=bucket_name, object_key="KEY_PLACEHOLDER", version_id="VERSION_ID_PLACEHOLDER")
+
     objects_data = []
     for obj in result.objects:
         objects_data.append({
@@ -450,13 +450,6 @@ def list_bucket_objects(bucket_name: str):
             "last_modified": obj.last_modified.isoformat(),
             "last_modified_display": obj.last_modified.strftime("%b %d, %Y %H:%M"),
             "etag": obj.etag,
-            "metadata": obj.metadata or {},
-            "preview_url": url_for("ui.object_preview", bucket_name=bucket_name, object_key=obj.key),
-            "download_url": url_for("ui.object_preview", bucket_name=bucket_name, object_key=obj.key) + "?download=1",
-            "presign_endpoint": url_for("ui.object_presign", bucket_name=bucket_name, object_key=obj.key),
-            "delete_endpoint": url_for("ui.delete_object", bucket_name=bucket_name, object_key=obj.key),
-            "versions_endpoint": url_for("ui.object_versions", bucket_name=bucket_name, object_key=obj.key),
-            "restore_template": url_for("ui.restore_object_version", bucket_name=bucket_name, object_key=obj.key, version_id="VERSION_ID_PLACEHOLDER"),
         })
 
     return jsonify({
@@ -465,6 +458,14 @@ def list_bucket_objects(bucket_name: str):
         "next_continuation_token": result.next_continuation_token,
         "total_count": result.total_count,
         "versioning_enabled": versioning_enabled,
+        "url_templates": {
+            "preview": preview_template,
+            "download": preview_template + "?download=1",
+            "presign": presign_template,
+            "delete": delete_template,
+            "versions": versions_template,
+            "restore": restore_template,
+        },
     })
 
 
@@ -738,41 +739,30 @@ def bulk_download_objects(bucket_name: str):
     unique_keys = list(dict.fromkeys(cleaned))
     storage = _storage()
     
-    # Check permissions for all keys first (or at least bucket read)
+    # Verify permission to read bucket contents
-    # We'll check bucket read once, then object read for each if needed?
-    # _authorize_ui checks bucket level if object_key is None, but we need to check each object if fine-grained policies exist.
-    # For simplicity/performance, we check bucket list/read.
     try:
         _authorize_ui(principal, bucket_name, "read")
     except IamError as exc:
         return jsonify({"error": str(exc)}), 403
 
-    # Create ZIP
+    # Create ZIP archive of selected objects
     buffer = io.BytesIO()
     with zipfile.ZipFile(buffer, "w", zipfile.ZIP_DEFLATED) as zf:
         for key in unique_keys:
             try:
-                # Verify individual object permission if needed? 
-                # _authorize_ui(principal, bucket_name, "read", object_key=key) 
-                # This might be slow for many objects. Assuming bucket read is enough for now or we accept the overhead.
-                # Let's skip individual check for bulk speed, assuming bucket read implies object read unless denied.
-                # But strictly we should check. Let's check.
                 _authorize_ui(principal, bucket_name, "read", object_key=key)
                 
-                # Check if object is encrypted
                 metadata = storage.get_object_metadata(bucket_name, key)
                 is_encrypted = "x-amz-server-side-encryption" in metadata
                 
                 if is_encrypted and hasattr(storage, 'get_object_data'):
-                    # Decrypt and add to zip
                     data, _ = storage.get_object_data(bucket_name, key)
                     zf.writestr(key, data)
                 else:
-                    # Add unencrypted file directly
                     path = storage.get_object_path(bucket_name, key)
                     zf.write(path, arcname=key)
             except (StorageError, IamError):
-                # Skip files we can't read or don't exist
+                # Skip objects that can't be accessed
                 continue
     
     buffer.seek(0)
@@ -1077,7 +1067,6 @@ def update_bucket_encryption(bucket_name: str):
     action = request.form.get("action", "enable")
     
     if action == "disable":
-        # Disable encryption
         try:
             _storage().set_bucket_encryption(bucket_name, None)
             flash("Default encryption disabled", "info")
@@ -1085,16 +1074,14 @@ def update_bucket_encryption(bucket_name: str):
             flash(_friendly_error_message(exc), "danger")
         return redirect(url_for("ui.bucket_detail", bucket_name=bucket_name, tab="properties"))
     
-    # Enable or update encryption
     algorithm = request.form.get("algorithm", "AES256")
     kms_key_id = request.form.get("kms_key_id", "").strip() or None
     
-    # Validate algorithm
     if algorithm not in ("AES256", "aws:kms"):
         flash("Invalid encryption algorithm", "danger")
         return redirect(url_for("ui.bucket_detail", bucket_name=bucket_name, tab="properties"))
     
-    # Build encryption config following AWS format
+    # Build encryption configuration in AWS S3 format
     encryption_config: dict[str, Any] = {
         "Rules": [
             {
@@ -1270,7 +1257,6 @@ def delete_iam_user(access_key: str):
         return redirect(url_for("ui.iam_dashboard"))
 
     if access_key == principal.access_key:
-        # Self-deletion
         try:
             _iam().delete_user(access_key)
             session.pop("credentials", None)
@@ -1352,6 +1338,9 @@ def create_connection():
 
 @ui_bp.post("/connections/test")
 def test_connection():
+    from botocore.config import Config as BotoConfig
+    from botocore.exceptions import ConnectTimeoutError, EndpointConnectionError, ReadTimeoutError
+    
     principal = _current_principal()
     try:
         _iam().authorize(principal, None, "iam:list_users")
@@ -1368,18 +1357,32 @@ def test_connection():
         return jsonify({"status": "error", "message": "Missing credentials"}), 400
 
     try:
+        config = BotoConfig(
+            connect_timeout=5,
+            read_timeout=10,
+            retries={'max_attempts': 1}
+        )
         s3 = boto3.client(
             "s3",
             endpoint_url=endpoint,
             aws_access_key_id=access_key,
             aws_secret_access_key=secret_key,
             region_name=region,
+            config=config,
         )
-        # Try to list buckets to verify credentials and endpoint
+
         s3.list_buckets()
         return jsonify({"status": "ok", "message": "Connection successful"})
+    except (ConnectTimeoutError, ReadTimeoutError):
+        return jsonify({"status": "error", "message": f"Connection timed out - endpoint may be down or unreachable: {endpoint}"}), 400
+    except EndpointConnectionError:
+        return jsonify({"status": "error", "message": f"Could not connect to endpoint: {endpoint}"}), 400
+    except ClientError as e:
+        error_code = e.response.get('Error', {}).get('Code', 'Unknown')
+        error_msg = e.response.get('Error', {}).get('Message', str(e))
+        return jsonify({"status": "error", "message": f"Connection failed ({error_code}): {error_msg}"}), 400
     except Exception as e:
-        return jsonify({"status": "error", "message": str(e)}), 400
+        return jsonify({"status": "error", "message": f"Connection failed: {str(e)}"}), 400
 
 
 @ui_bp.post("/connections/<connection_id>/update")
@@ -1440,7 +1443,6 @@ def update_bucket_replication(bucket_name: str):
         flash(str(exc), "danger")
         return redirect(url_for("ui.bucket_detail", bucket_name=bucket_name, tab="replication"))
     
-    # Check if user is admin (required for create/delete operations)
     is_admin = False
     try:
         _iam().authorize(principal, None, "iam:list_users")
@@ -1451,14 +1453,12 @@ def update_bucket_replication(bucket_name: str):
     action = request.form.get("action")
     
     if action == "delete":
-        # Admin only - remove configuration entirely
         if not is_admin:
             flash("Only administrators can remove replication configuration", "danger")
             return redirect(url_for("ui.bucket_detail", bucket_name=bucket_name, tab="replication"))
         _replication().delete_rule(bucket_name)
         flash("Replication configuration removed", "info")
     elif action == "pause":
-        # Users can pause - just set enabled=False
         rule = _replication().get_rule(bucket_name)
         if rule:
             rule.enabled = False
@@ -1467,16 +1467,20 @@ def update_bucket_replication(bucket_name: str):
         else:
             flash("No replication configuration to pause", "warning")
     elif action == "resume":
-        # Users can resume - just set enabled=True
+        from .replication import REPLICATION_MODE_ALL
         rule = _replication().get_rule(bucket_name)
         if rule:
             rule.enabled = True
             _replication().set_rule(rule)
+            # When resuming, sync any pending objects that accumulated while paused
+            if rule.mode == REPLICATION_MODE_ALL:
+                _replication().replicate_existing_objects(bucket_name)
+                flash("Replication resumed. Syncing pending objects in background.", "success")
+            else:
                 flash("Replication resumed", "success")
         else:
             flash("No replication configuration to resume", "warning")
     elif action == "create":
-        # Admin only - create new configuration
         if not is_admin:
             flash("Only administrators can configure replication settings", "danger")
             return redirect(url_for("ui.bucket_detail", bucket_name=bucket_name, tab="replication"))
@@ -1501,7 +1505,6 @@ def update_bucket_replication(bucket_name: str):
             )
             _replication().set_rule(rule)
             
-            # If mode is "all", trigger replication of existing objects
             if replication_mode == REPLICATION_MODE_ALL:
                 _replication().replicate_existing_objects(bucket_name)
                 flash("Replication configured. Existing objects are being replicated in the background.", "success")
@@ -1526,10 +1529,31 @@ def get_replication_status(bucket_name: str):
     if not rule:
         return jsonify({"error": "No replication rule"}), 404
     
-    # This is the slow operation - compute sync status by comparing buckets
+    connection = _connections().get(rule.target_connection_id)
+    endpoint_healthy = False
+    endpoint_error = None
+    if connection:
+        endpoint_healthy = _replication().check_endpoint_health(connection)
+        if not endpoint_healthy:
+            endpoint_error = f"Cannot reach endpoint: {connection.endpoint_url}"
+    else:
+        endpoint_error = "Target connection not found"
+    
+    stats = None
+    if endpoint_healthy:
         stats = _replication().get_sync_status(bucket_name)
+    
     if not stats:
-        return jsonify({"error": "Failed to compute status"}), 500
+        return jsonify({
+            "objects_synced": 0,
+            "objects_pending": 0,
+            "objects_orphaned": 0,
+            "bytes_synced": 0,
+            "last_sync_at": rule.stats.last_sync_at if rule.stats else None,
+            "last_sync_key": rule.stats.last_sync_key if rule.stats else None,
+            "endpoint_healthy": endpoint_healthy,
+            "endpoint_error": endpoint_error,
+        })
     
     return jsonify({
         "objects_synced": stats.objects_synced,
@@ -1538,6 +1562,28 @@ def get_replication_status(bucket_name: str):
         "bytes_synced": stats.bytes_synced,
         "last_sync_at": stats.last_sync_at,
         "last_sync_key": stats.last_sync_key,
+        "endpoint_healthy": endpoint_healthy,
+        "endpoint_error": endpoint_error,
+    })
+
+
+@ui_bp.get("/connections/<connection_id>/health")
+def check_connection_health(connection_id: str):
+    """Check if a connection endpoint is reachable."""
+    principal = _current_principal()
+    try:
+        _iam().authorize(principal, None, "iam:list_users")
+    except IamError:
+        return jsonify({"error": "Access denied"}), 403
+    
+    conn = _connections().get(connection_id)
+    if not conn:
+        return jsonify({"healthy": False, "error": "Connection not found"}), 404
+    
+    healthy = _replication().check_endpoint_health(conn)
+    return jsonify({
+        "healthy": healthy,
+        "error": None if healthy else f"Cannot reach endpoint: {conn.endpoint_url}"
     })
 
 
@@ -1558,7 +1604,6 @@ def connections_dashboard():
 def metrics_dashboard():
     principal = _current_principal()
     
-    # Metrics are restricted to admin users
     try:
         _iam().authorize(principal, None, "iam:list_users")
     except IamError:
@@ -1582,16 +1627,13 @@ def metrics_dashboard():
     total_bytes_used = 0
     total_versions = 0
     
-    # Note: Uses cached stats from storage layer to improve performance
     cache_ttl = current_app.config.get("BUCKET_STATS_CACHE_TTL", 60)
     for bucket in buckets:
         stats = storage.bucket_stats(bucket.name, cache_ttl=cache_ttl)
-        # Use totals which include archived versions
         total_objects += stats.get("total_objects", stats.get("objects", 0))
         total_bytes_used += stats.get("total_bytes", stats.get("bytes", 0))
         total_versions += stats.get("version_count", 0)
     
-    # Calculate system uptime
     boot_time = psutil.boot_time()
     uptime_seconds = time.time() - boot_time
     uptime_days = int(uptime_seconds / 86400)

app/version.py

@@ -1,7 +1,7 @@
 """Central location for the application version string."""
 from __future__ import annotations
 
-APP_VERSION = "0.1.8"
+APP_VERSION = "0.1.9"
 
 
 def get_version() -> str:

static/css/main.css

@@ -66,8 +66,28 @@ html {
 	color: var(--myfsio-muted) !important;
 }
 
-.table-responsive { border-radius: 0.5rem; overflow: hidden; }
+.table-responsive { 
+	border-radius: 0.5rem; 
+	overflow-x: auto; 
+	-webkit-overflow-scrolling: touch;
+}
 .message-stack { position: sticky; top: 1rem; z-index: 100; }
+
+/* Mobile-friendly table improvements */
+.table-responsive table {
+	min-width: 600px;
+}
+
+.table-responsive table th,
+.table-responsive table td {
+	white-space: nowrap;
+}
+
+/* Allow text wrapping for description columns */
+.table-responsive table td.text-wrap {
+	white-space: normal;
+	min-width: 200px;
+}
 code { font-size: 0.85rem; }
 
 code {
@@ -389,8 +409,22 @@ code {
 .bucket-table th:last-child { white-space: nowrap; }
 
 .object-key {
-	word-break: break-word;
+	max-width: 0;
-	max-width: 32rem;
+	width: 100%;
+	overflow: hidden;
+	text-overflow: ellipsis;
+}
+
+.object-key .fw-medium {
+	white-space: nowrap;
+	overflow: hidden;
+	text-overflow: ellipsis;
+}
+
+.object-key .text-muted {
+	white-space: nowrap;
+	overflow: hidden;
+	text-overflow: ellipsis;
 }
 
 .preview-card { top: 1rem; }
@@ -1553,6 +1587,41 @@ pre code {
 		position: relative !important;
 		top: 0 !important;
 	}
+	
+	/* Ensure tables are scrollable on mobile */
+	.card-body .table-responsive {
+		margin: -1rem;
+		padding: 0;
+		width: calc(100% + 2rem);
+	}
+	
+	.card-body .table-responsive table {
+		margin-bottom: 0;
+	}
+	
+	/* IAM users table mobile adjustments */
+	.table th,
+	.table td {
+		padding: 0.5rem 0.75rem;
+	}
+	
+	/* Better touch scrolling indicator */
+	.table-responsive::after {
+		content: '';
+		position: absolute;
+		top: 0;
+		right: 0;
+		bottom: 0;
+		width: 20px;
+		background: linear-gradient(to left, var(--myfsio-card-bg), transparent);
+		pointer-events: none;
+		opacity: 0;
+		transition: opacity 0.3s;
+	}
+	
+	.table-responsive:not(:hover)::after {
+		opacity: 0.8;
+	}
 }
 
 *:focus-visible {

templates/bucket_detail.html

@@ -134,15 +134,15 @@
         data-bulk-delete-endpoint="{{ url_for('ui.bulk_delete_objects', bucket_name=bucket_name) }}"
         data-bulk-download-endpoint="{{ url_for('ui.bulk_download_objects', bucket_name=bucket_name) }}"
       >
-        <table class="table table-hover align-middle mb-0" id="objects-table">
+        <table class="table table-hover align-middle mb-0" id="objects-table" style="table-layout: fixed;">
           <thead class="table-light">
             <tr>
               <th scope="col" class="text-center" style="width: 3rem;">
                 <input class="form-check-input" type="checkbox" data-select-all aria-label="Select all objects" />
               </th>
               <th scope="col">Key</th>
-              <th scope="col" class="text-end">Size</th>
+              <th scope="col" class="text-end" style="width: 6rem;">Size</th>
-              <th scope="col" class="text-end">Actions</th>
+              <th scope="col" class="text-end" style="width: 5.5rem;">Actions</th>
             </tr>
           </thead>
           <tbody>
@@ -172,15 +172,17 @@
           <button id="load-more-btn" class="btn btn-link btn-sm p-0 d-none" style="font-size: 0.75rem;">Load more</button>
         </div>
         <div class="d-flex align-items-center gap-1">
-          <span class="text-muted">Load</span>
+          <span class="text-muted">Batch</span>
-          <select id="page-size-select" class="form-select form-select-sm py-0" style="width: auto; font-size: 0.75rem;">
+          <select id="page-size-select" class="form-select form-select-sm py-0" style="width: auto; font-size: 0.75rem;" title="Number of objects to load per batch">
-            <option value="50">50</option>
+            <option value="1000">1K</option>
-            <option value="100" selected>100</option>
+            <option value="5000" selected>5K</option>
-            <option value="150">150</option>
+            <option value="10000">10K</option>
-            <option value="200">200</option>
+            <option value="25000">25K</option>
-            <option value="250">250</option>
+            <option value="50000">50K</option>
+            <option value="75000">75K</option>
+            <option value="100000">100K</option>
           </select>
-          <span class="text-muted">per page</span>
+          <span class="text-muted">per batch</span>
         </div>
       </div>
     </div>
@@ -954,7 +956,7 @@
             </div>
             <div class="card-body">
               {% if replication_rule and replication_rule.enabled %}
-              <div class="alert alert-success d-flex align-items-center mb-4" role="alert">
+              <div id="replication-status-alert" class="alert alert-success d-flex align-items-center mb-4" role="alert">
                 <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" fill="currentColor" class="bi bi-check-circle-fill flex-shrink-0 me-2" viewBox="0 0 16 16">
                   <path d="M16 8A8 8 0 1 1 0 8a8 8 0 0 1 16 0zm-3.97-3.03a.75.75 0 0 0-1.08.022L7.477 9.417 5.384 7.323a.75.75 0 0 0-1.06 1.06L6.97 11.03a.75.75 0 0 0 1.079-.02l3.992-4.99a.75.75 0 0 0-.01-1.05z"/>
                 </svg>
@@ -968,6 +970,19 @@
                 </div>
               </div>
               
+              <!-- Warning alert for unreachable endpoint (shown by JS if endpoint is down) -->
+              <div id="replication-endpoint-warning" class="alert alert-danger d-none mb-4" role="alert">
+                <div class="d-flex align-items-start">
+                  <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" fill="currentColor" class="flex-shrink-0 me-2" viewBox="0 0 16 16">
+                    <path d="M8.982 1.566a1.13 1.13 0 0 0-1.96 0L.165 13.233c-.457.778.091 1.767.98 1.767h13.713c.889 0 1.438-.99.98-1.767L8.982 1.566zM8 5c.535 0 .954.462.9.995l-.35 3.507a.552.552 0 0 1-1.1 0L7.1 5.995A.905.905 0 0 1 8 5zm.002 6a1 1 0 1 1 0 2 1 1 0 0 1 0-2z"/>
+                  </svg>
+                  <div>
+                    <strong>Replication Endpoint Unreachable</strong>
+                    <p class="mb-0 small" id="replication-endpoint-error">The target endpoint is not responding. Replication is paused until the endpoint is available.</p>
+                  </div>
+                </div>
+              </div>
+              
               <div class="row g-3 mb-4" id="replication-stats-cards" data-status-endpoint="{{ url_for('ui.get_replication_status', bucket_name=bucket_name) }}">
                 <div class="col-6 col-lg">
                   <div class="card bg-body-tertiary border-0 h-100">
@@ -1090,11 +1105,11 @@
                       {% endif %}
                     </div>
                     <div class="col-auto">
-                      <span class="badge bg-success-subtle text-success px-3 py-2">
+                      <span id="replication-status-badge" class="badge bg-success-subtle text-success px-3 py-2">
                         <svg xmlns="http://www.w3.org/2000/svg" width="12" height="12" fill="currentColor" class="me-1" viewBox="0 0 16 16">
                           <path d="M16 8A8 8 0 1 1 0 8a8 8 0 0 1 16 0zm-3.97-3.03a.75.75 0 0 0-1.08.022L7.477 9.417 5.384 7.323a.75.75 0 0 0-1.06 1.06L6.97 11.03a.75.75 0 0 0 1.079-.02l3.992-4.99a.75.75 0 0 0-.01-1.05z"/>
                         </svg>
-                        Enabled
+                        <span id="replication-status-text">Enabled</span>
                       </span>
                     </div>
                   </div>
@@ -1109,7 +1124,7 @@
                   </svg>
                   Refresh
                 </a>
-                <form method="POST" action="{{ url_for('ui.update_bucket_replication', bucket_name=bucket_name) }}" class="d-inline">
+                <form id="pause-replication-form" method="POST" action="{{ url_for('ui.update_bucket_replication', bucket_name=bucket_name) }}" class="d-inline">
                   <input type="hidden" name="csrf_token" value="{{ csrf_token() }}" />
                   <input type="hidden" name="action" value="pause">
                   <button type="submit" class="btn btn-outline-warning">
@@ -1131,13 +1146,18 @@
               </div>
 
               {% elif replication_rule and not replication_rule.enabled %}
-              <div class="alert alert-warning d-flex align-items-center mb-4" role="alert">
+              <div class="alert alert-warning d-flex align-items-start mb-4" role="alert">
-                <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" fill="currentColor" class="flex-shrink-0 me-2" viewBox="0 0 16 16">
+                <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" fill="currentColor" class="flex-shrink-0 me-2 mt-1" viewBox="0 0 16 16">
                   <path d="M5.5 3.5A1.5 1.5 0 0 1 7 5v6a1.5 1.5 0 0 1-3 0V5a1.5 1.5 0 0 1 1.5-1.5zm5 0A1.5 1.5 0 0 1 12 5v6a1.5 1.5 0 0 1-3 0V5a1.5 1.5 0 0 1 1.5-1.5z"/>
                 </svg>
                 <div>
-                  <strong>Replication Paused</strong> — 
+                  <strong>Replication Paused</strong>
-                  Replication is configured but currently paused. New uploads will not be replicated until resumed.
+                  <p class="mb-1">Replication is configured but currently paused. New uploads will not be replicated until resumed.</p>
+                  {% if replication_rule.mode == 'all' %}
+                  <p class="mb-0 small text-dark"><strong>Tip:</strong> When you resume, any objects uploaded while paused will be automatically synced to the target.</p>
+                  {% else %}
+                  <p class="mb-0 small text-dark"><strong>Note:</strong> Objects uploaded while paused will not be synced (mode: new_only). Consider switching to "All Objects" mode if you need to sync missed uploads.</p>
+                  {% endif %}
                 </div>
               </div>
               
@@ -1866,30 +1886,49 @@
   let isLoadingObjects = false;
   let hasMoreObjects = false;
   let currentFilterTerm = '';
-  let pageSize = 100;
+  let pageSize = 5000;  // Load large batches for virtual scrolling
+  let currentPrefix = '';  // Current folder prefix for navigation
+  let allObjects = [];  // All loaded object metadata (lightweight)
+  let urlTemplates = null;  // URL templates from API for constructing object URLs
 
-  const createObjectRow = (obj) => {
+  // Helper to build URL from template by replacing KEY_PLACEHOLDER with encoded key
+  const buildUrlFromTemplate = (template, key) => {
+    if (!template) return '';
+    return template.replace('KEY_PLACEHOLDER', encodeURIComponent(key).replace(/%2F/g, '/'));
+  };
+
+  // Virtual scrolling state
+  const ROW_HEIGHT = 53;  // Height of each table row in pixels
+  const BUFFER_ROWS = 10;  // Extra rows to render above/below viewport
+  let visibleItems = [];  // Current items to display (filtered by folder/search)
+  let renderedRange = { start: 0, end: 0 };  // Currently rendered row indices
+
+  // Create a row element from object data (for virtual scrolling)
+  const createObjectRow = (obj, displayKey = null) => {
     const tr = document.createElement('tr');
     tr.dataset.objectRow = '';
     tr.dataset.key = obj.key;
     tr.dataset.size = obj.size;
-    tr.dataset.lastModified = obj.last_modified;
+    tr.dataset.lastModified = obj.lastModified || obj.last_modified;
     tr.dataset.etag = obj.etag;
-    tr.dataset.previewUrl = obj.preview_url;
+    tr.dataset.previewUrl = obj.previewUrl || obj.preview_url;
-    tr.dataset.downloadUrl = obj.download_url;
+    tr.dataset.downloadUrl = obj.downloadUrl || obj.download_url;
-    tr.dataset.presignEndpoint = obj.presign_endpoint;
+    tr.dataset.presignEndpoint = obj.presignEndpoint || obj.presign_endpoint;
-    tr.dataset.deleteEndpoint = obj.delete_endpoint;
+    tr.dataset.deleteEndpoint = obj.deleteEndpoint || obj.delete_endpoint;
-    tr.dataset.metadata = JSON.stringify(obj.metadata || {});
+    tr.dataset.metadata = typeof obj.metadata === 'string' ? obj.metadata : JSON.stringify(obj.metadata || {});
-    tr.dataset.versionsEndpoint = obj.versions_endpoint;
+    tr.dataset.versionsEndpoint = obj.versionsEndpoint || obj.versions_endpoint;
-    tr.dataset.restoreTemplate = obj.restore_template;
+    tr.dataset.restoreTemplate = obj.restoreTemplate || obj.restore_template;
+    
+    const keyToShow = displayKey || obj.key;
+    const lastModDisplay = obj.lastModifiedDisplay || obj.last_modified_display || new Date(obj.lastModified || obj.last_modified).toLocaleDateString();
 
     tr.innerHTML = `
       <td class="text-center align-middle">
         <input class="form-check-input" type="checkbox" data-object-select aria-label="Select ${escapeHtml(obj.key)}" />
       </td>
       <td class="object-key text-break" title="${escapeHtml(obj.key)}">
-        <div class="fw-medium">${escapeHtml(obj.key)}</div>
+        <div class="fw-medium">${escapeHtml(keyToShow)}</div>
-        <div class="text-muted small">Modified ${escapeHtml(obj.last_modified_display)}</div>
+        <div class="text-muted small">Modified ${escapeHtml(lastModDisplay)}</div>
       </td>
       <td class="text-end text-nowrap">
         <span class="text-muted small">${formatBytes(obj.size)}</span>
@@ -1898,7 +1937,7 @@
         <div class="btn-group btn-group-sm" role="group">
           <a
             class="btn btn-outline-primary btn-icon"
-            href="${escapeHtml(obj.download_url)}"
+            href="${escapeHtml(obj.downloadUrl || obj.download_url)}"
             target="_blank"
             title="Download"
             aria-label="Download"
@@ -1987,12 +2026,180 @@
     }
   };
 
+  // ============== VIRTUAL SCROLLING SYSTEM ==============
+  
+  // Spacer elements for virtual scroll height
+  let topSpacer = null;
+  let bottomSpacer = null;
+  
+  const initVirtualScrollElements = () => {
+    if (!objectsTableBody) return;
+    
+    // Create spacer rows if they don't exist
+    if (!topSpacer) {
+      topSpacer = document.createElement('tr');
+      topSpacer.id = 'virtual-top-spacer';
+      topSpacer.innerHTML = '<td colspan="4" style="padding: 0; border: none;"></td>';
+    }
+    if (!bottomSpacer) {
+      bottomSpacer = document.createElement('tr');
+      bottomSpacer.id = 'virtual-bottom-spacer';
+      bottomSpacer.innerHTML = '<td colspan="4" style="padding: 0; border: none;"></td>';
+    }
+  };
+  
+  // Compute which items should be visible based on current view
+  const computeVisibleItems = () => {
+    const items = [];
+    const folders = new Set();
+    
+    allObjects.forEach(obj => {
+      if (!obj.key.startsWith(currentPrefix)) return;
+      
+      const remainder = obj.key.slice(currentPrefix.length);
+      const slashIndex = remainder.indexOf('/');
+      
+      if (slashIndex === -1) {
+        // File in current folder - filter on the displayed filename (remainder)
+        if (!currentFilterTerm || remainder.toLowerCase().includes(currentFilterTerm)) {
+          items.push({ type: 'file', data: obj, displayKey: remainder });
+        }
+      } else {
+        // Folder
+        const folderName = remainder.slice(0, slashIndex);
+        const folderPath = currentPrefix + folderName + '/';
+        if (!folders.has(folderPath)) {
+          folders.add(folderPath);
+          // Filter on the displayed folder name only
+          if (!currentFilterTerm || folderName.toLowerCase().includes(currentFilterTerm)) {
+            items.push({ type: 'folder', path: folderPath, displayKey: folderName });
+          }
+        }
+      }
+    });
+    
+    // Sort: folders first, then files
+    items.sort((a, b) => {
+      if (a.type === 'folder' && b.type === 'file') return -1;
+      if (a.type === 'file' && b.type === 'folder') return 1;
+      const aKey = a.type === 'folder' ? a.path : a.data.key;
+      const bKey = b.type === 'folder' ? b.path : b.data.key;
+      return aKey.localeCompare(bKey);
+    });
+    
+    return items;
+  };
+  
+  // Render only the visible rows based on scroll position
+  const renderVirtualRows = () => {
+    if (!objectsTableBody || !scrollContainer) return;
+    
+    const containerHeight = scrollContainer.clientHeight;
+    const scrollTop = scrollContainer.scrollTop;
+    
+    // Calculate visible range
+    const startIndex = Math.max(0, Math.floor(scrollTop / ROW_HEIGHT) - BUFFER_ROWS);
+    const endIndex = Math.min(visibleItems.length, Math.ceil((scrollTop + containerHeight) / ROW_HEIGHT) + BUFFER_ROWS);
+    
+    // Skip if range hasn't changed significantly
+    if (startIndex === renderedRange.start && endIndex === renderedRange.end) return;
+    
+    renderedRange = { start: startIndex, end: endIndex };
+    
+    // Clear and rebuild
+    objectsTableBody.innerHTML = '';
+    
+    // Add top spacer
+    initVirtualScrollElements();
+    topSpacer.querySelector('td').style.height = `${startIndex * ROW_HEIGHT}px`;
+    objectsTableBody.appendChild(topSpacer);
+    
+    // Render visible rows
+    for (let i = startIndex; i < endIndex; i++) {
+      const item = visibleItems[i];
+      if (!item) continue;
+      
+      let row;
+      if (item.type === 'folder') {
+        row = createFolderRow(item.path, item.displayKey);
+      } else {
+        row = createObjectRow(item.data, item.displayKey);
+      }
+      row.dataset.virtualIndex = i;
+      objectsTableBody.appendChild(row);
+    }
+    
+    // Add bottom spacer
+    const remainingRows = visibleItems.length - endIndex;
+    bottomSpacer.querySelector('td').style.height = `${remainingRows * ROW_HEIGHT}px`;
+    objectsTableBody.appendChild(bottomSpacer);
+    
+    // Re-attach handlers to new rows
+    attachRowHandlers();
+  };
+  
+  // Debounced scroll handler for virtual scrolling
+  let scrollTimeout = null;
+  const handleVirtualScroll = () => {
+    if (scrollTimeout) cancelAnimationFrame(scrollTimeout);
+    scrollTimeout = requestAnimationFrame(renderVirtualRows);
+  };
+  
+  // Refresh the virtual list (after data changes or navigation)
+  const refreshVirtualList = () => {
+    visibleItems = computeVisibleItems();
+    renderedRange = { start: -1, end: -1 };  // Force re-render
+    
+    if (visibleItems.length === 0) {
+      if (allObjects.length === 0 && !hasMoreObjects) {
+        showEmptyState();
+      } else {
+        // Empty folder
+        objectsTableBody.innerHTML = `
+          <tr>
+            <td colspan="4" class="py-5">
+              <div class="empty-state">
+                <div class="empty-state-icon mx-auto" style="width: 64px; height: 64px;">
+                  <svg xmlns="http://www.w3.org/2000/svg" width="28" height="28" fill="currentColor" viewBox="0 0 16 16">
+                    <path d="M9.828 3h3.982a2 2 0 0 1 1.992 2.181l-.637 7A2 2 0 0 1 13.174 14H2.825a2 2 0 0 1-1.991-1.819l-.637-7a1.99 1.99 0 0 1 .342-1.31L.5 3a2 2 0 0 1 2-2h3.672a2 2 0 0 1 1.414.586l.828.828A2 2 0 0 0 9.828 3zm-8.322.12C1.72 3.042 1.95 3 2.19 3h5.396l-.707-.707A1 1 0 0 0 6.172 2H2.5a1 1 0 0 0-1 .981l.006.139z"/>
+                  </svg>
+                </div>
+                <h6 class="mb-2">Empty folder</h6>
+                <p class="text-muted small mb-0">This folder contains no objects${hasMoreObjects ? ' yet. Loading more...' : '.'}</p>
+              </div>
+            </td>
+          </tr>
+        `;
+      }
+    } else {
+      renderVirtualRows();
+    }
+    
+    updateFolderViewStatus();
+  };
+  
+  // Update status bar
+  const updateFolderViewStatus = () => {
+    const folderViewStatusEl = document.getElementById('folder-view-status');
+    if (!folderViewStatusEl) return;
+    
+    if (currentPrefix) {
+      const folderCount = visibleItems.filter(i => i.type === 'folder').length;
+      const fileCount = visibleItems.filter(i => i.type === 'file').length;
+      folderViewStatusEl.innerHTML = `<span class="text-muted">${folderCount} folder${folderCount !== 1 ? 's' : ''}, ${fileCount} file${fileCount !== 1 ? 's' : ''} in this view</span>`;
+      folderViewStatusEl.classList.remove('d-none');
+    } else {
+      folderViewStatusEl.classList.add('d-none');
+    }
+  };
+
+  // ============== DATA LOADING ==============
+
   const loadObjects = async (append = false) => {
     if (isLoadingObjects) return;
     isLoadingObjects = true;
 
     if (!append) {
-
       if (objectsLoadingRow) objectsLoadingRow.style.display = '';
       nextContinuationToken = null;
       loadedObjectCount = 0;
@@ -2026,122 +2233,51 @@
       totalObjectCount = data.total_count || 0;
       nextContinuationToken = data.next_continuation_token;
 
-      if (!append) {
+      if (!append && objectsLoadingRow) {
-
+        objectsLoadingRow.remove();
-        if (objectsLoadingRow) objectsLoadingRow.remove();
-        
-        if (data.objects.length === 0) {
-          showEmptyState();
-          updateObjectCountBadge();
-          isLoadingObjects = false;
-          return;
       }
 
-        objectsTableBody.innerHTML = '';
+      if (data.url_templates && !urlTemplates) {
+        urlTemplates = data.url_templates;
       }
 
       data.objects.forEach(obj => {
-        const row = createObjectRow(obj);
-        objectsTableBody.appendChild(row);
         loadedObjectCount++;
-
+        const key = obj.key;
-        // Apply current filter to newly loaded objects
-        if (currentFilterTerm) {
-          const keyLower = obj.key.toLowerCase();
-          row.style.display = keyLower.includes(currentFilterTerm) ? '' : 'none';
-        }
-
         allObjects.push({
-          key: obj.key,
+          key: key,
           size: obj.size,
           lastModified: obj.last_modified,
+          lastModifiedDisplay: obj.last_modified_display,
           etag: obj.etag,
-          previewUrl: obj.preview_url,
+          previewUrl: urlTemplates ? buildUrlFromTemplate(urlTemplates.preview, key) : '',
-          downloadUrl: obj.download_url,
+          downloadUrl: urlTemplates ? buildUrlFromTemplate(urlTemplates.download, key) : '',
-          presignEndpoint: obj.presign_endpoint,
+          presignEndpoint: urlTemplates ? buildUrlFromTemplate(urlTemplates.presign, key) : '',
-          deleteEndpoint: obj.delete_endpoint,
+          deleteEndpoint: urlTemplates ? buildUrlFromTemplate(urlTemplates.delete, key) : '',
-          metadata: JSON.stringify(obj.metadata || {}),
+          metadata: '{}',
-          versionsEndpoint: obj.versions_endpoint,
+          versionsEndpoint: urlTemplates ? buildUrlFromTemplate(urlTemplates.versions, key) : '',
-          restoreTemplate: obj.restore_template,
+          restoreTemplate: urlTemplates ? urlTemplates.restore.replace('KEY_PLACEHOLDER', encodeURIComponent(key).replace(/%2F/g, '/')) : ''
-          element: row
         });
       });
 
       updateObjectCountBadge();
-
-      // Track if there are more objects to load
       hasMoreObjects = data.is_truncated;
       
       if (loadMoreStatus) {
         if (data.is_truncated) {
-          loadMoreStatus.textContent = `${loadedObjectCount.toLocaleString()} of ${totalObjectCount.toLocaleString()} objects loaded`;
+          loadMoreStatus.textContent = `${loadedObjectCount.toLocaleString()} of ${totalObjectCount.toLocaleString()} loaded`;
         } else {
-          loadMoreStatus.textContent = `All ${loadedObjectCount.toLocaleString()} objects loaded`;
+          loadMoreStatus.textContent = `${loadedObjectCount.toLocaleString()} objects`;
         }
       }
       
-      // Update Load More button visibility
       if (typeof updateLoadMoreButton === 'function') {
         updateLoadMoreButton();
       }
 
-      // Track the count of items in current folder before re-rendering
+      // Refresh virtual scroll view
-      let prevFolderItemCount = 0;
+      refreshVirtualList();
-      if (currentPrefix && append) {
+      renderBreadcrumb(currentPrefix);
-        const prevState = getFoldersAtPrefix(currentPrefix);
-        prevFolderItemCount = prevState.folders.length + prevState.files.length;
-      }
-
-      if (typeof initFolderNavigation === 'function') {
-        initFolderNavigation();
-      }
-
-      attachRowHandlers();
-
-      // If we're in a nested folder and loaded more objects, scroll to show newly loaded content
-      if (currentPrefix && append) {
-        const newState = getFoldersAtPrefix(currentPrefix);
-        const newFolderItemCount = newState.folders.length + newState.files.length;
-        const addedCount = newFolderItemCount - prevFolderItemCount;
-        
-        if (addedCount > 0) {
-          // Show a brief notification about newly loaded items in the current folder
-          const folderViewStatusEl = document.getElementById('folder-view-status');
-          if (folderViewStatusEl) {
-            folderViewStatusEl.innerHTML = `<span class="text-success fw-medium">+${addedCount} new item${addedCount !== 1 ? 's' : ''} loaded in this folder</span>`;
-            folderViewStatusEl.classList.remove('d-none');
-            // Reset to normal status after 3 seconds
-            setTimeout(() => {
-              if (typeof updateFolderViewStatus === 'function') {
-                updateFolderViewStatus();
-              }
-            }, 3000);
-          }
-          
-          // Scroll to show the first newly added item
-          const allRows = objectsTableBody.querySelectorAll('tr:not([style*="display: none"])');
-          if (allRows.length > prevFolderItemCount) {
-            const firstNewRow = allRows[prevFolderItemCount];
-            if (firstNewRow) {
-              firstNewRow.scrollIntoView({ behavior: 'smooth', block: 'center' });
-              // Briefly highlight the new rows
-              for (let i = prevFolderItemCount; i < allRows.length; i++) {
-                allRows[i].classList.add('table-info');
-                setTimeout(() => {
-                  allRows[i].classList.remove('table-info');
-                }, 2000);
-              }
-            }
-          }
-        } else if (hasMoreObjects) {
-          // Objects were loaded but none were in the current folder - show a hint
-          const folderViewStatusEl = document.getElementById('folder-view-status');
-          if (folderViewStatusEl) {
-            folderViewStatusEl.innerHTML = `<span class="text-muted">Loaded more objects (not in this folder). <button type="button" class="btn btn-link btn-sm p-0" onclick="navigateToFolder('')">Go to root</button> to see all.</span>`;
-            folderViewStatusEl.classList.remove('d-none');
-          }
-        }
-      }
 
     } catch (error) {
       console.error('Failed to load objects:', error);
@@ -2152,7 +2288,6 @@
       }
     } finally {
       isLoadingObjects = false;
-      // Hide loading spinner
       if (loadMoreSpinner) {
         loadMoreSpinner.classList.add('d-none');
       }
@@ -2160,16 +2295,15 @@
   };
 
   const attachRowHandlers = () => {
+    // Attach handlers to object rows
     const objectRows = document.querySelectorAll('[data-object-row]');
     objectRows.forEach(row => {
-
       if (row.dataset.handlersAttached) return;
       row.dataset.handlersAttached = 'true';
 
       const deleteBtn = row.querySelector('[data-delete-object]');
       deleteBtn?.addEventListener('click', (e) => {
         e.stopPropagation();
-
         const deleteModalEl = document.getElementById('deleteObjectModal');
         const deleteModal = deleteModalEl ? bootstrap.Modal.getOrCreateInstance(deleteModalEl) : null;
         const deleteObjectForm = document.getElementById('deleteObjectForm');
@@ -2186,17 +2320,63 @@
       selectCheckbox?.addEventListener('change', () => {
         toggleRowSelection(row, selectCheckbox.checked);
       });
+      
+      // Restore selection state
+      if (selectedRows.has(row.dataset.key)) {
+        selectCheckbox.checked = true;
+        row.classList.add('table-active');
+      }
+    });
+    
+    // Attach handlers to folder rows
+    const folderRows = document.querySelectorAll('.folder-row');
+    folderRows.forEach(row => {
+      if (row.dataset.handlersAttached) return;
+      row.dataset.handlersAttached = 'true';
+      
+      const folderPath = row.dataset.folderPath;
+      
+      const checkbox = row.querySelector('[data-folder-select]');
+      checkbox?.addEventListener('change', (e) => {
+        e.stopPropagation();
+        // Select all objects in this folder
+        const folderObjects = allObjects.filter(obj => obj.key.startsWith(folderPath));
+        folderObjects.forEach(obj => {
+          if (checkbox.checked) {
+            selectedRows.set(obj.key, obj);
+          } else {
+            selectedRows.delete(obj.key);
+          }
+        });
+        updateBulkDeleteState();
+      });
+
+      const folderBtn = row.querySelector('button');
+      folderBtn?.addEventListener('click', (e) => {
+        e.stopPropagation();
+        navigateToFolder(folderPath);
+      });
+      
+      row.addEventListener('click', (e) => {
+        if (e.target.closest('[data-folder-select]') || e.target.closest('button')) return;
+        navigateToFolder(folderPath);
+      });
     });
 
     updateBulkDeleteState();
   };
 
-  // Infinite scroll: use IntersectionObserver to auto-load more objects
+  // Scroll container reference (needed for virtual scrolling)
   const scrollSentinel = document.getElementById('scroll-sentinel');
   const scrollContainer = document.querySelector('.objects-table-container');
   const loadMoreBtn = document.getElementById('load-more-btn');
   
-  // Load More button click handler (fallback for mobile)
+  // Virtual scroll: listen to scroll events
+  if (scrollContainer) {
+    scrollContainer.addEventListener('scroll', handleVirtualScroll, { passive: true });
+  }
+  
+  // Load More button click handler (fallback)
   loadMoreBtn?.addEventListener('click', () => {
     if (hasMoreObjects && !isLoadingObjects) {
       loadObjects(true);
@@ -2210,8 +2390,8 @@
     }
   }
   
+  // Auto-load more when near bottom (for loading all data)
   if (scrollSentinel && scrollContainer) {
-    // Observer for scrolling within the container (desktop)
     const containerObserver = new IntersectionObserver((entries) => {
       entries.forEach(entry => {
         if (entry.isIntersecting && hasMoreObjects && !isLoadingObjects) {
@@ -2220,12 +2400,11 @@
       });
     }, {
       root: scrollContainer,
-      rootMargin: '100px',
+      rootMargin: '500px',  // Load more earlier for smoother experience
       threshold: 0
     });
     containerObserver.observe(scrollSentinel);
     
-    // Observer for page scrolling (mobile - when container is not scrollable)
     const viewportObserver = new IntersectionObserver((entries) => {
       entries.forEach(entry => {
         if (entry.isIntersecting && hasMoreObjects && !isLoadingObjects) {
@@ -2233,14 +2412,14 @@
         }
       });
     }, {
-      root: null, // viewport
+      root: null,
-      rootMargin: '200px',
+      rootMargin: '500px',
       threshold: 0
     });
     viewportObserver.observe(scrollSentinel);
   }
 
-  // Page size selector
+  // Page size selector (now controls batch size)
   const pageSizeSelect = document.getElementById('page-size-select');
   pageSizeSelect?.addEventListener('change', (e) => {
     pageSize = parseInt(e.target.value, 10);
@@ -2252,7 +2431,6 @@
 
   const folderBreadcrumb = document.getElementById('folder-breadcrumb');
   const objectsTableBody = document.querySelector('#objects-table tbody');
-  let currentPrefix = '';
 
   if (objectsTableBody) {
     objectsTableBody.addEventListener('click', (e) => {
@@ -2369,8 +2547,8 @@
     return allObjects.filter(obj => obj.key.startsWith(folderPrefix));
   };
 
-  const createFolderRow = (folderPath) => {
+  const createFolderRow = (folderPath, displayName = null) => {
-    const folderName = folderPath.slice(currentPrefix.length).replace(/\/$/, '');
+    const folderName = displayName || folderPath.slice(currentPrefix.length).replace(/\/$/, '');
     const { count: objectCount, mayHaveMore } = countObjectsInFolder(folderPath);
     const countDisplay = mayHaveMore ? `${objectCount}+` : objectCount;
     
@@ -2404,37 +2582,19 @@
       </td>
     `;
     
-    const checkbox = tr.querySelector('[data-folder-select]');
-    checkbox?.addEventListener('change', (e) => {
-      e.stopPropagation();
-      const folderObjects = getObjectsInFolder(folderPath);
-      folderObjects.forEach(obj => {
-        const objCheckbox = obj.element.querySelector('[data-object-select]');
-        if (objCheckbox) {
-          objCheckbox.checked = checkbox.checked;
-        }
-        toggleRowSelection(obj.element, checkbox.checked);
-      });
-    });
-
-    const folderBtn = tr.querySelector('button');
-    folderBtn?.addEventListener('click', (e) => {
-      e.stopPropagation();
-      navigateToFolder(folderPath);
-    });
-    
-    tr.addEventListener('click', (e) => {
-      if (e.target.closest('[data-folder-select]') || e.target.closest('button')) return;
-      navigateToFolder(folderPath);
-    });
-    
     return tr;
   };
 
+  // Instant client-side folder navigation (no server round-trip!)
   const navigateToFolder = (prefix) => {
     currentPrefix = prefix;
+    
+    // Scroll to top when navigating
+    if (scrollContainer) scrollContainer.scrollTop = 0;
+    
+    // Instant re-render from already-loaded data
+    refreshVirtualList();
     renderBreadcrumb(prefix);
-    renderObjectsView();
 
     selectedRows.clear();
 
@@ -2442,14 +2602,6 @@
       updateBulkDeleteState();
     }
 
-    if (typeof updateFolderViewStatus === 'function') {
-      updateFolderViewStatus();
-    }
-
-    if (typeof updateFilterWarning === 'function') {
-      updateFilterWarning();
-    }
-
     if (previewPanel) previewPanel.classList.add('d-none');
     if (previewEmpty) previewEmpty.classList.remove('d-none');
     activeRow = null;
@@ -2651,12 +2803,10 @@
       bulkDeleteConfirm.disabled = selectedCount === 0 || bulkDeleting;
     }
     if (selectAllCheckbox) {
-
+      // With virtual scrolling, count files in current folder from visibleItems
-      const visibleRowsRaw = hasFolders()
+      const filesInView = visibleItems.filter(item => item.type === 'file');
-        ? allObjects.filter(obj => obj.key.startsWith(currentPrefix) && !obj.key.slice(currentPrefix.length).includes('/')).map(obj => obj.element)
+      const total = filesInView.length;
-        : Array.from(document.querySelectorAll('[data-object-row]'));
+      const visibleSelectedCount = filesInView.filter(item => selectedRows.has(item.data.key)).length;
-      const total = visibleRowsRaw.filter(r => r.style.display !== 'none').length;
-      const visibleSelectedCount = visibleRowsRaw.filter(r => r.style.display !== 'none' && selectedRows.has(r.dataset.key)).length;
       selectAllCheckbox.disabled = total === 0;
       selectAllCheckbox.checked = visibleSelectedCount > 0 && visibleSelectedCount === total && total > 0;
       selectAllCheckbox.indeterminate = visibleSelectedCount > 0 && visibleSelectedCount < total;
@@ -3287,59 +3437,13 @@
     }
   };
 
-  const updateFolderViewStatus = () => {
-    if (!folderViewStatus || !loadMoreStatus) return;
-    if (currentPrefix) {
-      const { folders, files } = getFoldersAtPrefix(currentPrefix);
-      const visibleCount = folders.length + files.length;
-      const folderObjectCount = allObjects.filter(obj => obj.key.startsWith(currentPrefix)).length;
-      const folderMayHaveMore = hasMoreObjects && folderObjectCount > 0;
-      if (folderMayHaveMore) {
-        folderViewStatus.textContent = `Showing ${visibleCount} items in folder • more may be available`;
-        folderViewStatus.classList.remove('d-none');
-        loadMoreStatus.classList.add('d-none');
-      } else {
-        folderViewStatus.textContent = `${visibleCount} items in folder`;
-        folderViewStatus.classList.remove('d-none');
-        loadMoreStatus.classList.add('d-none');
-      }
-    } else {
-      folderViewStatus.classList.add('d-none');
-      loadMoreStatus.classList.remove('d-none');
-    }
-  };
-
   document.getElementById('object-search')?.addEventListener('input', (event) => {
     currentFilterTerm = event.target.value.toLowerCase();
     updateFilterWarning();
     
-    if (hasFolders()) {
+    // Use the virtual scrolling system for filtering - it properly handles
-      const { folders, files } = getFoldersAtPrefix(currentPrefix);
+    // both folder view and flat view, and works with large object counts
-      const tbody = objectsTableBody;
+    refreshVirtualList();
-
-      tbody.innerHTML = '';
-
-      folders.forEach(folderPath => {
-        const folderName = folderPath.slice(currentPrefix.length).replace(/\/$/, '').toLowerCase();
-        if (folderName.includes(currentFilterTerm)) {
-          tbody.appendChild(createFolderRow(folderPath));
-        }
-      });
-
-      files.forEach(obj => {
-        const keyName = obj.key.slice(currentPrefix.length).toLowerCase();
-        if (keyName.includes(currentFilterTerm)) {
-          tbody.appendChild(obj.element);
-          obj.element.style.display = '';
-        }
-      });
-    } else {
-      // Filter all loaded objects (including newly loaded ones)
-      document.querySelectorAll('[data-object-row]').forEach((row) => {
-        const key = row.dataset.key.toLowerCase();
-        row.style.display = key.includes(currentFilterTerm) ? '' : 'none';
-      });
-    }
   });
 
   refreshVersionsButton?.addEventListener('click', () => {
@@ -3698,40 +3802,39 @@
   selectAllCheckbox?.addEventListener('change', (event) => {
     const shouldSelect = Boolean(event.target?.checked);
 
-    if (hasFolders()) {
+    // Get all file items in the current view (works with virtual scrolling)
+    const filesInView = visibleItems.filter(item => item.type === 'file');
 
-      const objectsInCurrentView = allObjects.filter(obj => obj.key.startsWith(currentPrefix));
+    // Update selectedRows directly using object keys (not DOM elements)
-      objectsInCurrentView.forEach(obj => {
+    filesInView.forEach(item => {
-        const checkbox = obj.element.querySelector('[data-object-select]');
+      if (shouldSelect) {
-        if (checkbox && !checkbox.disabled) {
+        selectedRows.set(item.data.key, item.data);
-          checkbox.checked = shouldSelect;
+      } else {
+        selectedRows.delete(item.data.key);
       }
-        toggleRowSelection(obj.element, shouldSelect);
     });
 
+    // Update folder checkboxes in DOM (folders are always rendered)
     document.querySelectorAll('[data-folder-select]').forEach(cb => {
       cb.checked = shouldSelect;
     });
-    } else {
 
+    // Update any currently rendered object checkboxes
     document.querySelectorAll('[data-object-row]').forEach((row) => {
-        if (row.style.display === 'none') return;
       const checkbox = row.querySelector('[data-object-select]');
-        if (!checkbox || checkbox.disabled) {
+      if (checkbox) {
-          return;
-        }
         checkbox.checked = shouldSelect;
-        toggleRowSelection(row, shouldSelect);
-      });
       }
+    });
+
+    updateBulkDeleteState();
     setTimeout(updateBulkDownloadState, 0);
   });
 
   bulkDownloadButton?.addEventListener('click', async () => {
     if (!bulkDownloadEndpoint) return;
-    const selected = Array.from(document.querySelectorAll('[data-object-select]:checked')).map(
+    // Use selectedRows which tracks all selected objects (not just rendered ones)
-      (cb) => cb.closest('tr').dataset.key
+    const selected = Array.from(selectedRows.keys());
-    );
     if (selected.length === 0) return;
 
     bulkDownloadButton.disabled = true;
@@ -3780,6 +3883,12 @@
     const lastSyncEl = document.getElementById('replication-last-sync');
     const lastSyncTimeEl = document.querySelector('[data-stat="last-sync-time"]');
     const lastSyncKeyEl = document.querySelector('[data-stat="last-sync-key"]');
+    const endpointWarning = document.getElementById('replication-endpoint-warning');
+    const endpointErrorEl = document.getElementById('replication-endpoint-error');
+    const statusAlert = document.getElementById('replication-status-alert');
+    const statusBadge = document.getElementById('replication-status-badge');
+    const statusText = document.getElementById('replication-status-text');
+    const pauseForm = document.getElementById('pause-replication-form');
 
     const loadReplicationStats = async () => {
       try {
@@ -3787,6 +3896,48 @@
         if (!resp.ok) throw new Error('Failed to fetch stats');
         const data = await resp.json();
 
+        // Handle endpoint health status
+        if (data.endpoint_healthy === false) {
+          // Show warning and hide success alert
+          if (endpointWarning) {
+            endpointWarning.classList.remove('d-none');
+            if (endpointErrorEl && data.endpoint_error) {
+              endpointErrorEl.textContent = data.endpoint_error + '. Replication is paused until the endpoint is available.';
+            }
+          }
+          if (statusAlert) statusAlert.classList.add('d-none');
+          
+          // Update status badge to show "Paused" with warning styling
+          if (statusBadge) {
+            statusBadge.className = 'badge bg-warning-subtle text-warning px-3 py-2';
+            statusBadge.innerHTML = `
+              <svg xmlns="http://www.w3.org/2000/svg" width="12" height="12" fill="currentColor" class="me-1" viewBox="0 0 16 16">
+                <path d="M5.5 3.5A1.5 1.5 0 0 1 7 5v6a1.5 1.5 0 0 1-3 0V5a1.5 1.5 0 0 1 1.5-1.5zm5 0A1.5 1.5 0 0 1 12 5v6a1.5 1.5 0 0 1-3 0V5a1.5 1.5 0 0 1 1.5-1.5z"/>
+              </svg>
+              <span>Paused (Endpoint Unavailable)</span>`;
+          }
+          
+          // Hide the pause button since replication is effectively already paused
+          if (pauseForm) pauseForm.classList.add('d-none');
+        } else {
+          // Hide warning and show success alert
+          if (endpointWarning) endpointWarning.classList.add('d-none');
+          if (statusAlert) statusAlert.classList.remove('d-none');
+          
+          // Restore status badge to show "Enabled"
+          if (statusBadge) {
+            statusBadge.className = 'badge bg-success-subtle text-success px-3 py-2';
+            statusBadge.innerHTML = `
+              <svg xmlns="http://www.w3.org/2000/svg" width="12" height="12" fill="currentColor" class="me-1" viewBox="0 0 16 16">
+                <path d="M16 8A8 8 0 1 1 0 8a8 8 0 0 1 16 0zm-3.97-3.03a.75.75 0 0 0-1.08.022L7.477 9.417 5.384 7.323a.75.75 0 0 0-1.06 1.06L6.97 11.03a.75.75 0 0 0 1.079-.02l3.992-4.99a.75.75 0 0 0-.01-1.05z"/>
+              </svg>
+              <span>Enabled</span>`;
+          }
+          
+          // Show the pause button
+          if (pauseForm) pauseForm.classList.remove('d-none');
+        }
+
         if (syncedEl) syncedEl.textContent = data.objects_synced;
         if (pendingEl) {
           pendingEl.textContent = data.objects_pending;

templates/connections.html

@@ -104,6 +104,7 @@
                     <table class="table table-hover align-middle mb-0">
                         <thead class="table-light">
                             <tr>
+                                <th scope="col" style="width: 50px;">Status</th>
                                 <th scope="col">Name</th>
                                 <th scope="col">Endpoint</th>
                                 <th scope="col">Region</th>
@@ -113,7 +114,12 @@
                         </thead>
                         <tbody>
                             {% for conn in connections %}
-                            <tr>
+                            <tr data-connection-id="{{ conn.id }}">
+                                <td class="text-center">
+                                    <span class="connection-status" data-status="checking" title="Checking...">
+                                        <span class="spinner-border spinner-border-sm text-muted" role="status" style="width: 12px; height: 12px;"></span>
+                                    </span>
+                                </td>
                                 <td>
                                     <div class="d-flex align-items-center gap-2">
                                         <div class="connection-icon">
@@ -301,7 +307,11 @@
         const formData = new FormData(form);
         const data = Object.fromEntries(formData.entries());
         
-        resultDiv.innerHTML = '<div class="text-info"><span class="spinner-border spinner-border-sm" role="status" aria-hidden="true"></span> Testing...</div>';
+        resultDiv.innerHTML = '<div class="text-info"><span class="spinner-border spinner-border-sm" role="status" aria-hidden="true"></span> Testing connection...</div>';
+        
+        // Use AbortController to timeout client-side after 20 seconds
+        const controller = new AbortController();
+        const timeoutId = setTimeout(() => controller.abort(), 20000);
         
         try {
             const response = await fetch("{{ url_for('ui.test_connection') }}", {
@@ -310,17 +320,44 @@
                     "Content-Type": "application/json",
                     "X-CSRFToken": "{{ csrf_token() }}"
                 },
-                body: JSON.stringify(data)
+                body: JSON.stringify(data),
+                signal: controller.signal
             });
+            clearTimeout(timeoutId);
             
             const result = await response.json();
             if (response.ok) {
-                resultDiv.innerHTML = `<div class="text-success"><i class="bi bi-check-circle"></i> ${result.message}</div>`;
+                resultDiv.innerHTML = `<div class="text-success">
+                    <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="me-1" viewBox="0 0 16 16">
+                        <path d="M16 8A8 8 0 1 1 0 8a8 8 0 0 1 16 0zm-3.97-3.03a.75.75 0 0 0-1.08.022L7.477 9.417 5.384 7.323a.75.75 0 0 0-1.06 1.06L6.97 11.03a.75.75 0 0 0 1.079-.02l3.992-4.99a.75.75 0 0 0-.01-1.05z"/>
+                    </svg>
+                    ${result.message}
+                </div>`;
             } else {
-                resultDiv.innerHTML = `<div class="text-danger"><i class="bi bi-exclamation-circle"></i> ${result.message}</div>`;
+                resultDiv.innerHTML = `<div class="text-danger">
+                    <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="me-1" viewBox="0 0 16 16">
+                        <path d="M16 8A8 8 0 1 1 0 8a8 8 0 0 1 16 0zM5.354 4.646a.5.5 0 1 0-.708.708L7.293 8l-2.647 2.646a.5.5 0 0 0 .708.708L8 8.707l2.646 2.647a.5.5 0 0 0 .708-.708L8.707 8l2.647-2.646a.5.5 0 0 0-.708-.708L8 7.293 5.354 4.646z"/>
+                    </svg>
+                    ${result.message}
+                </div>`;
             }
         } catch (error) {
-            resultDiv.innerHTML = `<div class="text-danger"><i class="bi bi-exclamation-circle"></i> Connection failed</div>`;
+            clearTimeout(timeoutId);
+            if (error.name === 'AbortError') {
+                resultDiv.innerHTML = `<div class="text-danger">
+                    <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="me-1" viewBox="0 0 16 16">
+                        <path d="M16 8A8 8 0 1 1 0 8a8 8 0 0 1 16 0zM5.354 4.646a.5.5 0 1 0-.708.708L7.293 8l-2.647 2.646a.5.5 0 0 0 .708.708L8 8.707l2.646 2.647a.5.5 0 0 0 .708-.708L8.707 8l2.647-2.646a.5.5 0 0 0-.708-.708L8 7.293 5.354 4.646z"/>
+                    </svg>
+                    Connection test timed out - endpoint may be unreachable
+                </div>`;
+            } else {
+                resultDiv.innerHTML = `<div class="text-danger">
+                    <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="me-1" viewBox="0 0 16 16">
+                        <path d="M16 8A8 8 0 1 1 0 8a8 8 0 0 1 16 0zM5.354 4.646a.5.5 0 1 0-.708.708L7.293 8l-2.647 2.646a.5.5 0 0 0 .708.708L8 8.707l2.646 2.647a.5.5 0 0 0 .708-.708L8.707 8l2.647-2.646a.5.5 0 0 0-.708-.708L8 7.293 5.354 4.646z"/>
+                    </svg>
+                    Connection failed: Network error
+                </div>`;
+            }
         }
     }
 
@@ -358,5 +395,54 @@
         const form = document.getElementById('deleteConnectionForm');
         form.action = "{{ url_for('ui.delete_connection', connection_id='CONN_ID') }}".replace('CONN_ID', id);
     });
+
+    // Check connection health for each connection in the table
+    // Uses staggered requests to avoid overwhelming the server
+    async function checkConnectionHealth(connectionId, statusEl) {
+        try {
+            const controller = new AbortController();
+            const timeoutId = setTimeout(() => controller.abort(), 15000);
+            
+            const response = await fetch(`/ui/connections/${connectionId}/health`, {
+                signal: controller.signal
+            });
+            clearTimeout(timeoutId);
+            
+            const data = await response.json();
+            if (data.healthy) {
+                statusEl.innerHTML = `
+                    <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="text-success" viewBox="0 0 16 16">
+                        <path d="M16 8A8 8 0 1 1 0 8a8 8 0 0 1 16 0zm-3.97-3.03a.75.75 0 0 0-1.08.022L7.477 9.417 5.384 7.323a.75.75 0 0 0-1.06 1.06L6.97 11.03a.75.75 0 0 0 1.079-.02l3.992-4.99a.75.75 0 0 0-.01-1.05z"/>
+                    </svg>`;
+                statusEl.setAttribute('data-status', 'healthy');
+                statusEl.setAttribute('title', 'Connected');
+            } else {
+                statusEl.innerHTML = `
+                    <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="text-danger" viewBox="0 0 16 16">
+                        <path d="M16 8A8 8 0 1 1 0 8a8 8 0 0 1 16 0zM5.354 4.646a.5.5 0 1 0-.708.708L7.293 8l-2.647 2.646a.5.5 0 0 0 .708.708L8 8.707l2.646 2.647a.5.5 0 0 0 .708-.708L8.707 8l2.647-2.646a.5.5 0 0 0-.708-.708L8 7.293 5.354 4.646z"/>
+                    </svg>`;
+                statusEl.setAttribute('data-status', 'unhealthy');
+                statusEl.setAttribute('title', data.error || 'Unreachable');
+            }
+        } catch (error) {
+            statusEl.innerHTML = `
+                <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="text-warning" viewBox="0 0 16 16">
+                    <path d="M8.982 1.566a1.13 1.13 0 0 0-1.96 0L.165 13.233c-.457.778.091 1.767.98 1.767h13.713c.889 0 1.438-.99.98-1.767L8.982 1.566zM8 5c.535 0 .954.462.9.995l-.35 3.507a.552.552 0 0 1-1.1 0L7.1 5.995A.905.905 0 0 1 8 5zm.002 6a1 1 0 1 1 0 2 1 1 0 0 1 0-2z"/>
+                </svg>`;
+            statusEl.setAttribute('data-status', 'unknown');
+            statusEl.setAttribute('title', 'Could not check status');
+        }
+    }
+
+    // Stagger health checks to avoid all requests at once
+    const connectionRows = document.querySelectorAll('tr[data-connection-id]');
+    connectionRows.forEach((row, index) => {
+        const connectionId = row.getAttribute('data-connection-id');
+        const statusEl = row.querySelector('.connection-status');
+        if (statusEl) {
+            // Stagger requests by 200ms each
+            setTimeout(() => checkConnectionHealth(connectionId, statusEl), index * 200);
+        }
+    });
 </script>
 {% endblock %}

templates/docs.html

@@ -47,9 +47,9 @@ python run.py --mode ui
           <table class="table table-sm table-bordered small mb-0">
             <thead class="table-light">
               <tr>
-                <th>Variable</th>
+                <th style="min-width: 180px;">Variable</th>
-                <th>Default</th>
+                <th style="min-width: 120px;">Default</th>
-                <th>Description</th>
+                <th class="text-wrap" style="min-width: 250px;">Description</th>
               </tr>
             </thead>
             <tbody>
@@ -407,10 +407,62 @@ curl -X POST {{ api_base }}/presign/demo/notes.txt \
           <span class="docs-section-kicker">07</span>
           <h2 class="h4 mb-0">API Examples</h2>
         </div>
-        <p class="text-muted">Common operations using boto3.</p>
+        <p class="text-muted">Common operations using popular SDKs and tools.</p>
 
-        <h5 class="mt-4">Multipart Upload</h5>
+        <h3 class="h6 text-uppercase text-muted mt-4">Python (boto3)</h3>
-<pre><code class="language-python">import boto3
+<pre class="mb-4"><code class="language-python">import boto3
+
+s3 = boto3.client(
+    's3',
+    endpoint_url='{{ api_base }}',
+    aws_access_key_id='&lt;access_key&gt;',
+    aws_secret_access_key='&lt;secret_key&gt;'
+)
+
+# List buckets
+buckets = s3.list_buckets()['Buckets']
+
+# Create bucket
+s3.create_bucket(Bucket='mybucket')
+
+# Upload file
+s3.upload_file('local.txt', 'mybucket', 'remote.txt')
+
+# Download file
+s3.download_file('mybucket', 'remote.txt', 'downloaded.txt')
+
+# Generate presigned URL (valid 1 hour)
+url = s3.generate_presigned_url(
+    'get_object',
+    Params={'Bucket': 'mybucket', 'Key': 'remote.txt'},
+    ExpiresIn=3600
+)</code></pre>
+
+        <h3 class="h6 text-uppercase text-muted mt-4">JavaScript (AWS SDK v3)</h3>
+<pre class="mb-4"><code class="language-javascript">import { S3Client, ListBucketsCommand, PutObjectCommand } from '@aws-sdk/client-s3';
+
+const s3 = new S3Client({
+  endpoint: '{{ api_base }}',
+  region: 'us-east-1',
+  credentials: {
+    accessKeyId: '&lt;access_key&gt;',
+    secretAccessKey: '&lt;secret_key&gt;'
+  },
+  forcePathStyle: true  // Required for S3-compatible services
+});
+
+// List buckets
+const { Buckets } = await s3.send(new ListBucketsCommand({}));
+
+// Upload object
+await s3.send(new PutObjectCommand({
+  Bucket: 'mybucket',
+  Key: 'hello.txt',
+  Body: 'Hello, World!'
+}));</code></pre>
+
+        <h3 class="h6 text-uppercase text-muted mt-4">Multipart Upload (Python)</h3>
+<pre class="mb-4"><code class="language-python">import boto3
 
 s3 = boto3.client('s3', endpoint_url='{{ api_base }}')
 
@@ -418,9 +470,9 @@ s3 = boto3.client('s3', endpoint_url='{{ api_base }}')
 response = s3.create_multipart_upload(Bucket='mybucket', Key='large.bin')
 upload_id = response['UploadId']
 
-# Upload parts
+# Upload parts (minimum 5MB each, except last part)
 parts = []
-chunks = [b'chunk1', b'chunk2'] # Example data chunks
+chunks = [b'chunk1...', b'chunk2...']
 for part_number, chunk in enumerate(chunks, start=1):
     response = s3.upload_part(
         Bucket='mybucket',
@@ -438,6 +490,19 @@ s3.complete_multipart_upload(
     UploadId=upload_id,
     MultipartUpload={'Parts': parts}
 )</code></pre>
+
+        <h3 class="h6 text-uppercase text-muted mt-4">Presigned URLs for Sharing</h3>
+<pre class="mb-0"><code class="language-bash"># Generate a download link valid for 15 minutes
+curl -X POST "{{ api_base }}/presign/mybucket/photo.jpg" \
+  -H "Content-Type: application/json" \
+  -H "X-Access-Key: &lt;key&gt;" -H "X-Secret-Key: &lt;secret&gt;" \
+  -d '{"method": "GET", "expires_in": 900}'
+
+# Generate an upload link (PUT) valid for 1 hour
+curl -X POST "{{ api_base }}/presign/mybucket/upload.bin" \
+  -H "Content-Type: application/json" \
+  -H "X-Access-Key: &lt;key&gt;" -H "X-Secret-Key: &lt;secret&gt;" \
+  -d '{"method": "PUT", "expires_in": 3600}'</code></pre>
       </div>
     </article>
     <article id="replication" class="card shadow-sm docs-section">
@@ -487,6 +552,86 @@ s3.complete_multipart_upload(
         </p>
       </div>
     </article>
+    <article id="versioning" class="card shadow-sm docs-section">
+      <div class="card-body">
+        <div class="d-flex align-items-center gap-2 mb-3">
+          <span class="docs-section-kicker">09</span>
+          <h2 class="h4 mb-0">Object Versioning</h2>
+        </div>
+        <p class="text-muted">Keep multiple versions of objects to protect against accidental deletions and overwrites. Restore previous versions at any time.</p>
+
+        <h3 class="h6 text-uppercase text-muted mt-4">Enabling Versioning</h3>
+        <ol class="docs-steps mb-3">
+          <li>Navigate to your bucket's <strong>Properties</strong> tab.</li>
+          <li>Find the <strong>Versioning</strong> card and click <strong>Enable</strong>.</li>
+          <li>All subsequent uploads will create new versions instead of overwriting.</li>
+        </ol>
+
+        <h3 class="h6 text-uppercase text-muted mt-4">Version Operations</h3>
+        <div class="table-responsive mb-3">
+          <table class="table table-sm table-bordered small">
+            <thead class="table-light">
+              <tr>
+                <th>Operation</th>
+                <th>Description</th>
+              </tr>
+            </thead>
+            <tbody>
+              <tr>
+                <td><strong>View Versions</strong></td>
+                <td>Click the version icon on any object to see all historical versions with timestamps and sizes.</td>
+              </tr>
+              <tr>
+                <td><strong>Restore Version</strong></td>
+                <td>Click <strong>Restore</strong> on any version to make it the current version (creates a copy).</td>
+              </tr>
+              <tr>
+                <td><strong>Delete Current</strong></td>
+                <td>Deleting an object archives it. Previous versions remain accessible.</td>
+              </tr>
+              <tr>
+                <td><strong>Purge All</strong></td>
+                <td>Permanently delete an object and all its versions. This cannot be undone.</td>
+              </tr>
+            </tbody>
+          </table>
+        </div>
+
+        <h3 class="h6 text-uppercase text-muted mt-4">Archived Objects</h3>
+        <p class="small text-muted mb-3">When you delete a versioned object, it becomes "archived" - the current version is removed but historical versions remain. The <strong>Archived</strong> tab shows these objects so you can restore them.</p>
+
+        <h3 class="h6 text-uppercase text-muted mt-4">API Usage</h3>
+<pre class="mb-3"><code class="language-bash"># Enable versioning
+curl -X PUT "{{ api_base }}/&lt;bucket&gt;?versioning" \
+  -H "Content-Type: application/json" \
+  -H "X-Access-Key: &lt;key&gt;" -H "X-Secret-Key: &lt;secret&gt;" \
+  -d '{"Status": "Enabled"}'
+
+# Get versioning status
+curl "{{ api_base }}/&lt;bucket&gt;?versioning" \
+  -H "X-Access-Key: &lt;key&gt;" -H "X-Secret-Key: &lt;secret&gt;"
+
+# List object versions
+curl "{{ api_base }}/&lt;bucket&gt;?versions" \
+  -H "X-Access-Key: &lt;key&gt;" -H "X-Secret-Key: &lt;secret&gt;"
+
+# Get specific version
+curl "{{ api_base }}/&lt;bucket&gt;/&lt;key&gt;?versionId=&lt;version-id&gt;" \
+  -H "X-Access-Key: &lt;key&gt;" -H "X-Secret-Key: &lt;secret&gt;"</code></pre>
+
+        <div class="alert alert-light border mb-0">
+          <div class="d-flex gap-2">
+            <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-info-circle text-muted mt-1" viewBox="0 0 16 16">
+              <path d="M8 15A7 7 0 1 1 8 1a7 7 0 0 1 0 14zm0 1A8 8 0 1 0 8 0a8 8 0 0 0 0 16z"/>
+              <path d="m8.93 6.588-2.29.287-.082.38.45.083c.294.07.352.176.288.469l-.738 3.468c-.194.897.105 1.319.808 1.319.545 0 1.178-.252 1.465-.598l.088-.416c-.2.176-.492.246-.686.246-.275 0-.375-.193-.304-.533L8.93 6.588zM9 4.5a1 1 0 1 1-2 0 1 1 0 0 1 2 0z"/>
+            </svg>
+            <div>
+              <strong>Storage Impact:</strong> Each version consumes storage. Enable quotas to limit total bucket size including all versions.
+            </div>
+          </div>
+        </div>
+      </div>
+    </article>
     <article id="quotas" class="card shadow-sm docs-section">
       <div class="card-body">
         <div class="d-flex align-items-center gap-2 mb-3">
@@ -709,6 +854,7 @@ curl -X DELETE "{{ api_base }}/kms/keys/{key-id}?waiting_period_days=30" \
           <li><a href="#api">REST endpoints</a></li>
           <li><a href="#examples">API Examples</a></li>
           <li><a href="#replication">Site Replication</a></li>
+          <li><a href="#versioning">Object Versioning</a></li>
           <li><a href="#quotas">Bucket Quotas</a></li>
           <li><a href="#encryption">Encryption</a></li>
           <li><a href="#troubleshooting">Troubleshooting</a></li>

tests/test_ui_pagination.py

@@ -157,9 +157,14 @@ class TestPaginatedObjectListing:
             assert "last_modified" in obj
             assert "last_modified_display" in obj
             assert "etag" in obj
-            assert "preview_url" in obj
+
-            assert "download_url" in obj
+            # URLs are now returned as templates (not per-object) for performance
-            assert "delete_endpoint" in obj
+            assert "url_templates" in data
+            templates = data["url_templates"]
+            assert "preview" in templates
+            assert "download" in templates
+            assert "delete" in templates
+            assert "KEY_PLACEHOLDER" in templates["preview"]
     
     def test_bucket_detail_page_loads_without_objects(self, tmp_path):
         """Bucket detail page should load even with many objects."""