app/bucket_policies.py

@@ -2,10 +2,12 @@
 from __future__ import annotations
 
 import json
+import re
+import time
 from dataclasses import dataclass
-from fnmatch import fnmatch
+from fnmatch import fnmatch, translate
 from pathlib import Path
-from typing import Any, Dict, Iterable, List, Optional, Sequence
+from typing import Any, Dict, Iterable, List, Optional, Pattern, Sequence, Tuple
 
 
 RESOURCE_PREFIX = "arn:aws:s3:::"
@@ -133,7 +135,22 @@ class BucketPolicyStatement:
     effect: str
     principals: List[str] | str
     actions: List[str]
-    resources: List[tuple[str | None, str | None]]
+    resources: List[Tuple[str | None, str | None]]
+    # Performance: Pre-compiled regex patterns for resource matching
+    _compiled_patterns: List[Tuple[str | None, Optional[Pattern[str]]]] | None = None
+
+    def _get_compiled_patterns(self) -> List[Tuple[str | None, Optional[Pattern[str]]]]:
+        """Lazily compile fnmatch patterns to regex for faster matching."""
+        if self._compiled_patterns is None:
+            self._compiled_patterns = []
+            for resource_bucket, key_pattern in self.resources:
+                if key_pattern is None:
+                    self._compiled_patterns.append((resource_bucket, None))
+                else:
+                    # Convert fnmatch pattern to regex
+                    regex_pattern = translate(key_pattern)
+                    self._compiled_patterns.append((resource_bucket, re.compile(regex_pattern)))
+        return self._compiled_patterns
 
     def matches_principal(self, access_key: Optional[str]) -> bool:
         if self.principals == "*":
@@ -149,15 +166,16 @@ class BucketPolicyStatement:
     def matches_resource(self, bucket: Optional[str], object_key: Optional[str]) -> bool:
         bucket = (bucket or "*").lower()
         key = object_key or ""
-        for resource_bucket, key_pattern in self.resources:
+        for resource_bucket, compiled_pattern in self._get_compiled_patterns():
             resource_bucket = (resource_bucket or "*").lower()
             if resource_bucket not in {"*", bucket}:
                 continue
-            if key_pattern is None:
+            if compiled_pattern is None:
                 if not key:
                     return True
                 continue
-            if fnmatch(key, key_pattern):
+            # Performance: Use pre-compiled regex instead of fnmatch
+            if compiled_pattern.match(key):
                 return True
         return False
 
@@ -174,8 +192,16 @@ class BucketPolicyStore:
         self._policies: Dict[str, List[BucketPolicyStatement]] = {}
         self._load()
         self._last_mtime = self._current_mtime()
+        # Performance: Avoid stat() on every request
+        self._last_stat_check = 0.0
+        self._stat_check_interval = 1.0  # Only check mtime every 1 second
 
     def maybe_reload(self) -> None:
+        # Performance: Skip stat check if we checked recently
+        now = time.time()
+        if now - self._last_stat_check < self._stat_check_interval:
+            return
+        self._last_stat_check = now
         current = self._current_mtime()
         if current is None or current == self._last_mtime:
             return

app/encrypted_storage.py

@@ -79,7 +79,7 @@ class EncryptedObjectStorage:
         kms_key_id: Optional[str] = None,
     ) -> ObjectMeta:
         """Store an object, optionally with encryption.
-        
+
         Args:
             bucket_name: Name of the bucket
             object_key: Key for the object
@@ -87,42 +87,41 @@ class EncryptedObjectStorage:
             metadata: Optional user metadata
             server_side_encryption: Encryption algorithm ("AES256" or "aws:kms")
             kms_key_id: KMS key ID (for aws:kms encryption)
-        
+
         Returns:
             ObjectMeta with object information
+
+        Performance: Uses streaming encryption for large files to reduce memory usage.
         """
         should_encrypt, algorithm, detected_kms_key = self._should_encrypt(
             bucket_name, server_side_encryption
         )
-        
+
         if kms_key_id is None:
             kms_key_id = detected_kms_key
-        
+
         if should_encrypt:
-            data = stream.read()
-            
             try:
-                ciphertext, enc_metadata = self.encryption.encrypt_object(
-                    data, 
+                # Performance: Use streaming encryption to avoid loading entire file into memory
+                encrypted_stream, enc_metadata = self.encryption.encrypt_stream(
+                    stream,
                     algorithm=algorithm,
-                    kms_key_id=kms_key_id,
                     context={"bucket": bucket_name, "key": object_key},
                 )
-                
+
                 combined_metadata = metadata.copy() if metadata else {}
                 combined_metadata.update(enc_metadata.to_dict())
-                
-                encrypted_stream = io.BytesIO(ciphertext)
+
                 result = self.storage.put_object(
                     bucket_name,
                     object_key,
                     encrypted_stream,
                     metadata=combined_metadata,
                 )
-                
+
                 result.metadata = combined_metadata
                 return result
-                
+
             except EncryptionError as exc:
                 raise StorageError(f"Encryption failed: {exc}") from exc
         else:
@@ -135,33 +134,34 @@ class EncryptedObjectStorage:
     
     def get_object_data(self, bucket_name: str, object_key: str) -> tuple[bytes, Dict[str, str]]:
         """Get object data, decrypting if necessary.
-        
+
         Returns:
             Tuple of (data, metadata)
+
+        Performance: Uses streaming decryption to reduce memory usage.
         """
         path = self.storage.get_object_path(bucket_name, object_key)
         metadata = self.storage.get_object_metadata(bucket_name, object_key)
-        
-        with path.open("rb") as f:
-            data = f.read()
-        
+
         enc_metadata = EncryptionMetadata.from_dict(metadata)
         if enc_metadata:
             try:
-                data = self.encryption.decrypt_object(
-                    data,
-                    enc_metadata,
-                    context={"bucket": bucket_name, "key": object_key},
-                )
+                # Performance: Use streaming decryption to avoid loading entire file into memory
+                with path.open("rb") as f:
+                    decrypted_stream = self.encryption.decrypt_stream(f, enc_metadata)
+                    data = decrypted_stream.read()
             except EncryptionError as exc:
                 raise StorageError(f"Decryption failed: {exc}") from exc
-        
+        else:
+            with path.open("rb") as f:
+                data = f.read()
+
         clean_metadata = {
             k: v for k, v in metadata.items()
-            if not k.startswith("x-amz-encryption") 
+            if not k.startswith("x-amz-encryption")
             and k != "x-amz-encrypted-data-key"
         }
-        
+
         return data, clean_metadata
     
     def get_object_stream(self, bucket_name: str, object_key: str) -> tuple[BinaryIO, Dict[str, str], int]:

app/encryption.py

@@ -183,81 +183,94 @@ class StreamingEncryptor:
         self.chunk_size = chunk_size
     
     def _derive_chunk_nonce(self, base_nonce: bytes, chunk_index: int) -> bytes:
-        """Derive a unique nonce for each chunk."""
-        # XOR the base nonce with the chunk index
-        nonce_int = int.from_bytes(base_nonce, "big")
-        derived = nonce_int ^ chunk_index
-        return derived.to_bytes(12, "big")
-    
-    def encrypt_stream(self, stream: BinaryIO, 
-                       context: Dict[str, str] | None = None) -> tuple[BinaryIO, EncryptionMetadata]:
-        """Encrypt a stream and return encrypted stream + metadata."""
+        """Derive a unique nonce for each chunk.
 
+        Performance: Use direct byte manipulation instead of full int conversion.
+        """
+        # Performance: Only modify last 4 bytes instead of full 12-byte conversion
+        return base_nonce[:8] + (chunk_index ^ int.from_bytes(base_nonce[8:], "big")).to_bytes(4, "big")
+
+    def encrypt_stream(self, stream: BinaryIO,
+                       context: Dict[str, str] | None = None) -> tuple[BinaryIO, EncryptionMetadata]:
+        """Encrypt a stream and return encrypted stream + metadata.
+
+        Performance: Writes chunks directly to output buffer instead of accumulating in list.
+        """
         data_key, encrypted_data_key = self.provider.generate_data_key()
         base_nonce = secrets.token_bytes(12)
-        
+
         aesgcm = AESGCM(data_key)
-        encrypted_chunks = []
+        # Performance: Write directly to BytesIO instead of accumulating chunks
+        output = io.BytesIO()
+        output.write(b"\x00\x00\x00\x00")  # Placeholder for chunk count
         chunk_index = 0
-        
+
         while True:
             chunk = stream.read(self.chunk_size)
             if not chunk:
                 break
-            
+
             chunk_nonce = self._derive_chunk_nonce(base_nonce, chunk_index)
             encrypted_chunk = aesgcm.encrypt(chunk_nonce, chunk, None)
-            
-            size_prefix = len(encrypted_chunk).to_bytes(self.HEADER_SIZE, "big")
-            encrypted_chunks.append(size_prefix + encrypted_chunk)
+
+            # Write size prefix + encrypted chunk directly
+            output.write(len(encrypted_chunk).to_bytes(self.HEADER_SIZE, "big"))
+            output.write(encrypted_chunk)
             chunk_index += 1
-        
-        header = chunk_index.to_bytes(4, "big")
-        encrypted_data = header + b"".join(encrypted_chunks)
-        
+
+        # Write actual chunk count to header
+        output.seek(0)
+        output.write(chunk_index.to_bytes(4, "big"))
+        output.seek(0)
+
         metadata = EncryptionMetadata(
             algorithm="AES256",
             key_id=self.provider.KEY_ID if hasattr(self.provider, "KEY_ID") else "local",
             nonce=base_nonce,
             encrypted_data_key=encrypted_data_key,
         )
-        
-        return io.BytesIO(encrypted_data), metadata
-    
+
+        return output, metadata
+
     def decrypt_stream(self, stream: BinaryIO, metadata: EncryptionMetadata) -> BinaryIO:
-        """Decrypt a stream using the provided metadata."""
+        """Decrypt a stream using the provided metadata.
+
+        Performance: Writes chunks directly to output buffer instead of accumulating in list.
+        """
         if isinstance(self.provider, LocalKeyEncryption):
             data_key = self.provider._decrypt_data_key(metadata.encrypted_data_key)
         else:
             raise EncryptionError("Unsupported provider for streaming decryption")
-        
+
         aesgcm = AESGCM(data_key)
         base_nonce = metadata.nonce
-        
+
         chunk_count_bytes = stream.read(4)
         if len(chunk_count_bytes) < 4:
             raise EncryptionError("Invalid encrypted stream: missing header")
         chunk_count = int.from_bytes(chunk_count_bytes, "big")
-        
-        decrypted_chunks = []
+
+        # Performance: Write directly to BytesIO instead of accumulating chunks
+        output = io.BytesIO()
         for chunk_index in range(chunk_count):
             size_bytes = stream.read(self.HEADER_SIZE)
             if len(size_bytes) < self.HEADER_SIZE:
                 raise EncryptionError(f"Invalid encrypted stream: truncated at chunk {chunk_index}")
             chunk_size = int.from_bytes(size_bytes, "big")
-            
+
             encrypted_chunk = stream.read(chunk_size)
             if len(encrypted_chunk) < chunk_size:
                 raise EncryptionError(f"Invalid encrypted stream: incomplete chunk {chunk_index}")
-            
+
             chunk_nonce = self._derive_chunk_nonce(base_nonce, chunk_index)
             try:
                 decrypted_chunk = aesgcm.decrypt(chunk_nonce, encrypted_chunk, None)
-                decrypted_chunks.append(decrypted_chunk)
+                output.write(decrypted_chunk)  # Write directly instead of appending to list
             except Exception as exc:
                 raise EncryptionError(f"Failed to decrypt chunk {chunk_index}: {exc}") from exc
-        
-        return io.BytesIO(b"".join(decrypted_chunks))
+
+        output.seek(0)
+        return output
 
 
 class EncryptionManager:

app/iam.py

@@ -4,11 +4,12 @@ from __future__ import annotations
 import json
 import math
 import secrets
+import time
 from collections import deque
 from dataclasses import dataclass
 from datetime import datetime, timedelta, timezone
 from pathlib import Path
-from typing import Any, Deque, Dict, Iterable, List, Optional, Sequence, Set
+from typing import Any, Deque, Dict, Iterable, List, Optional, Sequence, Set, Tuple
 
 
 class IamError(RuntimeError):
@@ -115,13 +116,24 @@ class IamService:
         self._raw_config: Dict[str, Any] = {}
         self._failed_attempts: Dict[str, Deque[datetime]] = {}
         self._last_load_time = 0.0
+        # Performance: credential cache with TTL
+        self._credential_cache: Dict[str, Tuple[str, Principal, float]] = {}
+        self._cache_ttl = 60.0  # Cache credentials for 60 seconds
+        self._last_stat_check = 0.0
+        self._stat_check_interval = 1.0  # Only stat() file every 1 second
         self._load()
 
     def _maybe_reload(self) -> None:
         """Reload configuration if the file has changed on disk."""
+        # Performance: Skip stat check if we checked recently
+        now = time.time()
+        if now - self._last_stat_check < self._stat_check_interval:
+            return
+        self._last_stat_check = now
         try:
             if self.config_path.stat().st_mtime > self._last_load_time:
                 self._load()
+                self._credential_cache.clear()  # Invalidate cache on reload
         except OSError:
             pass
 
@@ -181,17 +193,37 @@ class IamService:
         return int(max(0, self.auth_lockout_window.total_seconds() - elapsed))
 
     def principal_for_key(self, access_key: str) -> Principal:
+        # Performance: Check cache first
+        now = time.time()
+        cached = self._credential_cache.get(access_key)
+        if cached:
+            secret, principal, cached_time = cached
+            if now - cached_time < self._cache_ttl:
+                return principal
+
         self._maybe_reload()
         record = self._users.get(access_key)
         if not record:
             raise IamError("Unknown access key")
-        return self._build_principal(access_key, record)
+        principal = self._build_principal(access_key, record)
+        self._credential_cache[access_key] = (record["secret_key"], principal, now)
+        return principal
 
     def secret_for_key(self, access_key: str) -> str:
+        # Performance: Check cache first
+        now = time.time()
+        cached = self._credential_cache.get(access_key)
+        if cached:
+            secret, principal, cached_time = cached
+            if now - cached_time < self._cache_ttl:
+                return secret
+
         self._maybe_reload()
         record = self._users.get(access_key)
         if not record:
             raise IamError("Unknown access key")
+        principal = self._build_principal(access_key, record)
+        self._credential_cache[access_key] = (record["secret_key"], principal, now)
         return record["secret_key"]
 
     def authorize(self, principal: Principal, bucket_name: str | None, action: str) -> None:
@@ -442,11 +474,36 @@ class IamService:
         raise IamError("User not found")
 
     def get_secret_key(self, access_key: str) -> str | None:
+        # Performance: Check cache first
+        now = time.time()
+        cached = self._credential_cache.get(access_key)
+        if cached:
+            secret, principal, cached_time = cached
+            if now - cached_time < self._cache_ttl:
+                return secret
+
         self._maybe_reload()
         record = self._users.get(access_key)
-        return record["secret_key"] if record else None
+        if record:
+            # Cache the result
+            principal = self._build_principal(access_key, record)
+            self._credential_cache[access_key] = (record["secret_key"], principal, now)
+            return record["secret_key"]
+        return None
 
     def get_principal(self, access_key: str) -> Principal | None:
+        # Performance: Check cache first
+        now = time.time()
+        cached = self._credential_cache.get(access_key)
+        if cached:
+            secret, principal, cached_time = cached
+            if now - cached_time < self._cache_ttl:
+                return principal
+
         self._maybe_reload()
         record = self._users.get(access_key)
-        return self._build_principal(access_key, record) if record else None
+        if record:
+            principal = self._build_principal(access_key, record)
+            self._credential_cache[access_key] = (record["secret_key"], principal, now)
+            return principal
+        return None

app/s3_api.py

@@ -2171,48 +2171,89 @@ def _copy_object(dest_bucket: str, dest_key: str, copy_source: str) -> Response:
 
 
 class AwsChunkedDecoder:
-    """Decodes aws-chunked encoded streams."""
+    """Decodes aws-chunked encoded streams.
+
+    Performance optimized with buffered line reading instead of byte-by-byte.
+    """
+
     def __init__(self, stream):
         self.stream = stream
-        self.buffer = b""
+        self._read_buffer = bytearray()  # Performance: Pre-allocated buffer
         self.chunk_remaining = 0
         self.finished = False
 
+    def _read_line(self) -> bytes:
+        """Read until CRLF using buffered reads instead of byte-by-byte.
+
+        Performance: Reads in batches of 64-256 bytes instead of 1 byte at a time.
+        """
+        line = bytearray()
+        while True:
+            # Check if we have data in buffer
+            if self._read_buffer:
+                # Look for CRLF in buffer
+                idx = self._read_buffer.find(b"\r\n")
+                if idx != -1:
+                    # Found CRLF - extract line and update buffer
+                    line.extend(self._read_buffer[: idx + 2])
+                    del self._read_buffer[: idx + 2]
+                    return bytes(line)
+                # No CRLF yet - consume entire buffer
+                line.extend(self._read_buffer)
+                self._read_buffer.clear()
+
+            # Read more data in larger chunks (64 bytes is enough for chunk headers)
+            chunk = self.stream.read(64)
+            if not chunk:
+                return bytes(line) if line else b""
+            self._read_buffer.extend(chunk)
+
+    def _read_exact(self, n: int) -> bytes:
+        """Read exactly n bytes, using buffer first."""
+        result = bytearray()
+        # Use buffered data first
+        if self._read_buffer:
+            take = min(len(self._read_buffer), n)
+            result.extend(self._read_buffer[:take])
+            del self._read_buffer[:take]
+            n -= take
+
+        # Read remaining directly from stream
+        if n > 0:
+            data = self.stream.read(n)
+            if data:
+                result.extend(data)
+
+        return bytes(result)
+
     def read(self, size=-1):
         if self.finished:
             return b""
 
-        result = b""
+        result = bytearray()  # Performance: Use bytearray for building result
         while size == -1 or len(result) < size:
             if self.chunk_remaining > 0:
                 to_read = self.chunk_remaining
                 if size != -1:
                     to_read = min(to_read, size - len(result))
-                
-                chunk = self.stream.read(to_read)
+
+                chunk = self._read_exact(to_read)
                 if not chunk:
                     raise IOError("Unexpected EOF in chunk data")
-                
-                result += chunk
+
+                result.extend(chunk)
                 self.chunk_remaining -= len(chunk)
-                
+
                 if self.chunk_remaining == 0:
-                    crlf = self.stream.read(2)
+                    crlf = self._read_exact(2)
                     if crlf != b"\r\n":
                         raise IOError("Malformed chunk: missing CRLF")
             else:
-                line = b""
-                while True:
-                    char = self.stream.read(1)
-                    if not char:
-                        if not line:
-                            self.finished = True
-                            return result
-                        raise IOError("Unexpected EOF in chunk size")
-                    line += char
-                    if line.endswith(b"\r\n"):
-                        break
-                
+                line = self._read_line()
+                if not line:
+                    self.finished = True
+                    return bytes(result)
+
                 try:
                     line_str = line.decode("ascii").strip()
                     if ";" in line_str:
@@ -2223,22 +2264,16 @@ class AwsChunkedDecoder:
 
                 if chunk_size == 0:
                     self.finished = True
+                    # Skip trailing headers
                     while True:
-                        line = b""
-                        while True:
-                            char = self.stream.read(1)
-                            if not char:
-                                break
-                            line += char
-                            if line.endswith(b"\r\n"):
-                                break
-                        if line == b"\r\n" or not line:
+                        trailer = self._read_line()
+                        if trailer == b"\r\n" or not trailer:
                             break
-                    return result
-                
+                    return bytes(result)
+
                 self.chunk_remaining = chunk_size
-        
-        return result
+
+        return bytes(result)
 
 
 def _initiate_multipart_upload(bucket_name: str, object_key: str) -> Response:

app/storage.py

@@ -139,9 +139,21 @@ class ObjectStorage:
         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()
+        self._cache_lock = threading.Lock()  # Global lock for cache structure
+        # Performance: Per-bucket locks to reduce contention
+        self._bucket_locks: Dict[str, threading.Lock] = {}
         # Cache version counter for detecting stale reads
         self._cache_version: Dict[str, int] = {}
+        # Performance: Bucket config cache with TTL
+        self._bucket_config_cache: Dict[str, tuple[dict[str, Any], float]] = {}
+        self._bucket_config_cache_ttl = 30.0  # 30 second TTL
+
+    def _get_bucket_lock(self, bucket_id: str) -> threading.Lock:
+        """Get or create a lock for a specific bucket. Reduces global lock contention."""
+        with self._cache_lock:
+            if bucket_id not in self._bucket_locks:
+                self._bucket_locks[bucket_id] = threading.Lock()
+            return self._bucket_locks[bucket_id]
 
     def list_buckets(self) -> List[BucketMeta]:
         buckets: List[BucketMeta] = []
@@ -247,11 +259,13 @@ class ObjectStorage:
         bucket_path = self._bucket_path(bucket_name)
         if not bucket_path.exists():
             raise StorageError("Bucket does not exist")
-        if self._has_visible_objects(bucket_path):
+        # Performance: Single check instead of three separate traversals
+        has_objects, has_versions, has_multipart = self._check_bucket_contents(bucket_path)
+        if has_objects:
             raise StorageError("Bucket not empty")
-        if self._has_archived_versions(bucket_path):
+        if has_versions:
             raise StorageError("Bucket contains archived object versions")
-        if self._has_active_multipart_uploads(bucket_path):
+        if has_multipart:
             raise StorageError("Bucket has active multipart uploads")
         self._remove_tree(bucket_path)
         self._remove_tree(self._system_bucket_root(bucket_path.name))
@@ -393,17 +407,20 @@ class ObjectStorage:
         internal_meta = {"__etag__": etag, "__size__": str(stat.st_size)}
         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(
+
+        # Performance: Lazy update - only update the affected key instead of invalidating whole cache
+        obj_meta = ObjectMeta(
             key=safe_key.as_posix(),
             size=stat.st_size,
             last_modified=datetime.fromtimestamp(stat.st_mtime, timezone.utc),
             etag=etag,
             metadata=metadata,
         )
+        self._update_object_cache_entry(bucket_id, safe_key.as_posix(), obj_meta)
+
+        return obj_meta
 
     def get_object_path(self, bucket_name: str, object_key: str) -> Path:
         path = self._object_path(bucket_name, object_key)
@@ -449,9 +466,10 @@ class ObjectStorage:
         rel = path.relative_to(bucket_path)
         self._safe_unlink(path)
         self._delete_metadata(bucket_id, rel)
-        
+
         self._invalidate_bucket_stats_cache(bucket_id)
-        self._invalidate_object_cache(bucket_id)
+        # Performance: Lazy update - only remove the affected key instead of invalidating whole cache
+        self._update_object_cache_entry(bucket_id, safe_key.as_posix(), None)
         self._cleanup_empty_parents(path, bucket_path)
 
     def purge_object(self, bucket_name: str, object_key: str) -> None:
@@ -471,9 +489,10 @@ class ObjectStorage:
         legacy_version_dir = self._legacy_version_dir(bucket_id, rel)
         if legacy_version_dir.exists():
             shutil.rmtree(legacy_version_dir, ignore_errors=True)
-        
+
         self._invalidate_bucket_stats_cache(bucket_id)
-        self._invalidate_object_cache(bucket_id)
+        # Performance: Lazy update - only remove the affected key instead of invalidating whole cache
+        self._update_object_cache_entry(bucket_id, rel.as_posix(), None)
         self._cleanup_empty_parents(target, bucket_path)
 
     def is_versioning_enabled(self, bucket_name: str) -> bool:
@@ -1054,16 +1073,19 @@ 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(
+        # Performance: Lazy update - only update the affected key instead of invalidating whole cache
+        obj_meta = ObjectMeta(
             key=safe_key.as_posix(),
             size=stat.st_size,
             last_modified=datetime.fromtimestamp(stat.st_mtime, timezone.utc),
             etag=checksum.hexdigest(),
             metadata=metadata,
         )
+        self._update_object_cache_entry(bucket_id, safe_key.as_posix(), obj_meta)
+
+        return obj_meta
 
     def abort_multipart_upload(self, bucket_name: str, upload_id: str) -> None:
         bucket_path = self._bucket_path(bucket_name)
@@ -1305,37 +1327,47 @@ class ObjectStorage:
         """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.
+        Thread-safe with per-bucket locks to reduce contention.
         """
         now = time.time()
 
+        # Quick check with global lock (brief)
         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
+            cache_version = self._cache_version.get(bucket_id, 0)
 
-        # Build cache outside lock to avoid holding lock during I/O
-        objects = self._build_object_cache(bucket_path)
+        # Use per-bucket lock for cache building (allows parallel builds for different buckets)
+        bucket_lock = self._get_bucket_lock(bucket_id)
+        with bucket_lock:
+            # Double-check cache after acquiring per-bucket lock
+            with self._cache_lock:
+                cached = self._object_cache.get(bucket_id)
+                if cached:
+                    objects, timestamp = cached
+                    if now - timestamp < self.KEY_INDEX_CACHE_TTL:
+                        self._object_cache.move_to_end(bucket_id)
+                        return objects
 
-        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)
+            # Build cache with per-bucket lock held (prevents duplicate work)
+            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)
+            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:
+                    objects = self._build_object_cache(bucket_path)
 
-            self._object_cache[bucket_id] = (objects, time.time())
-            self._object_cache.move_to_end(bucket_id)
+                # 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
 
@@ -1354,6 +1386,23 @@ class ObjectStorage:
         except OSError:
             pass
 
+    def _update_object_cache_entry(self, bucket_id: str, key: str, meta: Optional[ObjectMeta]) -> None:
+        """Update a single entry in the object cache instead of invalidating the whole cache.
+
+        This is a performance optimization - lazy update instead of full invalidation.
+        """
+        with self._cache_lock:
+            cached = self._object_cache.get(bucket_id)
+            if cached:
+                objects, timestamp = cached
+                if meta is None:
+                    # Delete operation - remove key from cache
+                    objects.pop(key, None)
+                else:
+                    # Put operation - update/add key in cache
+                    objects[key] = meta
+                # Keep same timestamp - don't reset TTL for single key updates
+
     def _ensure_system_roots(self) -> None:
         for path in (
             self._system_root_path(),
@@ -1373,19 +1422,33 @@ class ObjectStorage:
         return self._system_bucket_root(bucket_name) / self.BUCKET_CONFIG_FILE
 
     def _read_bucket_config(self, bucket_name: str) -> dict[str, Any]:
+        # Performance: Check cache first
+        now = time.time()
+        cached = self._bucket_config_cache.get(bucket_name)
+        if cached:
+            config, cached_time = cached
+            if now - cached_time < self._bucket_config_cache_ttl:
+                return config.copy()  # Return copy to prevent mutation
+
         config_path = self._bucket_config_path(bucket_name)
         if not config_path.exists():
+            self._bucket_config_cache[bucket_name] = ({}, now)
             return {}
         try:
             data = json.loads(config_path.read_text(encoding="utf-8"))
-            return data if isinstance(data, dict) else {}
+            config = data if isinstance(data, dict) else {}
+            self._bucket_config_cache[bucket_name] = (config, now)
+            return config.copy()
         except (OSError, json.JSONDecodeError):
+            self._bucket_config_cache[bucket_name] = ({}, now)
             return {}
 
     def _write_bucket_config(self, bucket_name: str, payload: dict[str, Any]) -> None:
         config_path = self._bucket_config_path(bucket_name)
         config_path.parent.mkdir(parents=True, exist_ok=True)
         config_path.write_text(json.dumps(payload), encoding="utf-8")
+        # Performance: Update cache immediately after write
+        self._bucket_config_cache[bucket_name] = (payload.copy(), time.time())
 
     def _set_bucket_config_entry(self, bucket_name: str, key: str, value: Any | None) -> None:
         config = self._read_bucket_config(bucket_name)
@@ -1507,33 +1570,68 @@ class ObjectStorage:
             except OSError:
                 continue
 
-    def _has_visible_objects(self, bucket_path: Path) -> bool:
+    def _check_bucket_contents(self, bucket_path: Path) -> tuple[bool, bool, bool]:
+        """Check bucket for objects, versions, and multipart uploads in a single pass.
+
+        Performance optimization: Combines three separate rglob traversals into one.
+        Returns (has_visible_objects, has_archived_versions, has_active_multipart_uploads).
+        Uses early exit when all three are found.
+        """
+        has_objects = False
+        has_versions = False
+        has_multipart = False
+        bucket_name = bucket_path.name
+
+        # Check visible objects in bucket
         for path in bucket_path.rglob("*"):
+            if has_objects:
+                break
             if not path.is_file():
                 continue
             rel = path.relative_to(bucket_path)
             if rel.parts and rel.parts[0] in self.INTERNAL_FOLDERS:
                 continue
-            return True
-        return False
+            has_objects = True
+
+        # Check archived versions (only if needed)
+        for version_root in (
+            self._bucket_versions_root(bucket_name),
+            self._legacy_versions_root(bucket_name),
+        ):
+            if has_versions:
+                break
+            if version_root.exists():
+                for path in version_root.rglob("*"):
+                    if path.is_file():
+                        has_versions = True
+                        break
+
+        # Check multipart uploads (only if needed)
+        for uploads_root in (
+            self._multipart_bucket_root(bucket_name),
+            self._legacy_multipart_bucket_root(bucket_name),
+        ):
+            if has_multipart:
+                break
+            if uploads_root.exists():
+                for path in uploads_root.rglob("*"):
+                    if path.is_file():
+                        has_multipart = True
+                        break
+
+        return has_objects, has_versions, has_multipart
+
+    def _has_visible_objects(self, bucket_path: Path) -> bool:
+        has_objects, _, _ = self._check_bucket_contents(bucket_path)
+        return has_objects
 
     def _has_archived_versions(self, bucket_path: Path) -> bool:
-        for version_root in (
-            self._bucket_versions_root(bucket_path.name),
-            self._legacy_versions_root(bucket_path.name),
-        ):
-            if version_root.exists() and any(path.is_file() for path in version_root.rglob("*")):
-                return True
-        return False
+        _, has_versions, _ = self._check_bucket_contents(bucket_path)
+        return has_versions
 
     def _has_active_multipart_uploads(self, bucket_path: Path) -> bool:
-        for uploads_root in (
-            self._multipart_bucket_root(bucket_path.name),
-            self._legacy_multipart_bucket_root(bucket_path.name),
-        ):
-            if uploads_root.exists() and any(path.is_file() for path in uploads_root.rglob("*")):
-                return True
-        return False
+        _, _, has_multipart = self._check_bucket_contents(bucket_path)
+        return has_multipart
 
     def _remove_tree(self, path: Path) -> None:
         if not path.exists():

templates/bucket_detail.html

@@ -2026,7 +2026,7 @@
             title="Download"
             aria-label="Download"
           >
-            <svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" fill="currentColor" class="bi bi-download" viewBox="0 0 16 16" aria-hidden="true">
+            <svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" fill="#0d6efd" class="bi bi-download" viewBox="0 0 16 16" aria-hidden="true">
               <path d="M.5 9.9a.5.5 0 0 1 .5.5v2.5a1 1 0 0 0 1 1h12a1 1 0 0 0 1-1v-2.5a.5.5 0 0 1 1 0v2.5a2 2 0 0 1-2 2H2a2 2 0 0 1-2-2v-2.5a.5.5 0 0 1 .5-.5z" />
               <path d="M7.646 11.854a.5.5 0 0 0 .708 0l3-3a.5.5 0 0 0-.708-.708L8.5 10.293V1.5a.5.5 0 0 0-1 0v8.793L5.354 8.146a.5.5 0 1 0-.708.708l3 3z" />
             </svg>
@@ -2038,7 +2038,7 @@
             title="Delete"
             aria-label="Delete"
           >
-            <svg xmlns="http://www.w3.org/2000/svg" width="13" height="13" fill="currentColor" class="bi bi-trash" viewBox="0 0 16 16" aria-hidden="true">
+            <svg xmlns="http://www.w3.org/2000/svg" width="13" height="13" fill="#dc3545" class="bi bi-trash" viewBox="0 0 16 16" aria-hidden="true">
               <path d="M5.5 5.5a.5.5 0 0 1 .5.5v6a.5.5 0 0 1-1 0v-6a.5.5 0 0 1 .5-.5zm2.5 0a.5.5 0 0 1 .5.5v6a.5.5 0 0 1-1 0v-6a.5.5 0 0 1 .5-.5zm3 .5v6a.5.5 0 0 1-1 0v-6a.5.5 0 0 1 1 0z" />
               <path fill-rule="evenodd" d="M14.5 3a1 1 0 0 1-1 1H13v9a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V4h-.5a1 1 0 0 1-1-1V2a1 1 0 0 1 1-1H6a1 1 0 0 1 1-1h2a1 1 0 0 1 1 1h3.5a1 1 0 0 1 1 1v1zM4.118 4 4 4.059V13a1 1 0 0 0 1 1h6a1 1 0 0 0 1-1V4.059L11.882 4H4.118zM2.5 3V2h11v1h-11z" />
             </svg>