diff --git a/backend/app/api/auth.py b/backend/app/api/auth.py
index 5461ed5..8e02f34 100644
--- a/backend/app/api/auth.py
+++ b/backend/app/api/auth.py
@@ -7,14 +7,14 @@ from app.auth.jwt import create_access_token
 from app.auth.repository import UserRepository
 from app.auth.schemas import TokenResponse, UserCreate, UserLogin, UserResponse
 from app.auth.security import validate_password_strength, verify_password
-from app.core.deps import get_current_user, get_db
+from app.core.deps import get_current_user, get_db_sync
 from app.database.models.user import User
 
 router = APIRouter(prefix="/auth", tags=["auth"])
 
 
 @router.post("/register", response_model=UserResponse, status_code=status.HTTP_201_CREATED)
-def register_user(user_data: UserCreate, db: Session = Depends(get_db)):
+def register_user(user_data: UserCreate, db: Session = Depends(get_db_sync)):
     """
     Register a new user.
 
@@ -46,7 +46,7 @@ def register_user(user_data: UserCreate, db: Session = Depends(get_db)):
 
 
 @router.post("/login", response_model=TokenResponse)
-def login_user(login_data: UserLogin, db: Session = Depends(get_db)):
+def login_user(login_data: UserLogin, db: Session = Depends(get_db_sync)):
     """
     Login user and return JWT token.
 
diff --git a/backend/app/api/images.py b/backend/app/api/images.py
index 2c94049..17a5261 100644
--- a/backend/app/api/images.py
+++ b/backend/app/api/images.py
@@ -3,9 +3,10 @@
 from uuid import UUID
 
 from fastapi import APIRouter, Depends, File, HTTPException, UploadFile, status
-from sqlalchemy.orm import Session
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
 
-from app.core.deps import get_current_user, get_db
+from app.core.deps import get_current_user_async, get_db
 from app.database.models.board import Board
 from app.database.models.user import User
 from app.images.processing import generate_thumbnails
@@ -30,7 +31,7 @@ router = APIRouter(prefix="/images", tags=["images"])
 @router.post("/upload", response_model=ImageUploadResponse, status_code=status.HTTP_201_CREATED)
 async def upload_image(
     file: UploadFile = File(...),
-    current_user: User = Depends(get_current_user),
+    current_user: User = Depends(get_current_user_async),
     db: AsyncSession = Depends(get_db),
 ):
     """
@@ -64,7 +65,7 @@ async def upload_image(
     checksum = calculate_checksum(contents)
 
     # Create metadata
-    metadata = {"format": mime_type.split("/")[1], "checksum": checksum, "thumbnails": thumbnail_paths}
+    image_metadata = {"format": mime_type.split("/")[1], "checksum": checksum, "thumbnails": thumbnail_paths}
 
     # Create database record
     repo = ImageRepository(db)
@@ -76,7 +77,7 @@ async def upload_image(
         mime_type=mime_type,
         width=width,
         height=height,
-        metadata=metadata,
+        image_metadata=image_metadata,
     )
 
     return image
@@ -85,7 +86,7 @@ async def upload_image(
 @router.post("/upload-zip", response_model=list[ImageUploadResponse])
 async def upload_zip(
     file: UploadFile = File(...),
-    current_user: User = Depends(get_current_user),
+    current_user: User = Depends(get_current_user_async),
     db: AsyncSession = Depends(get_db),
 ):
     """
@@ -120,7 +121,7 @@ async def upload_zip(
             checksum = calculate_checksum(contents)
 
             # Create metadata
-            metadata = {
+            img_metadata = {
                 "format": mime_type.split("/")[1],
                 "checksum": checksum,
                 "thumbnails": thumbnail_paths,
@@ -135,7 +136,7 @@ async def upload_zip(
                 mime_type=mime_type,
                 width=width,
                 height=height,
-                metadata=metadata,
+                image_metadata=img_metadata,
             )
 
             uploaded_images.append(image)
@@ -155,7 +156,7 @@ async def upload_zip(
 async def get_image_library(
     page: int = 1,
     page_size: int = 50,
-    current_user: User = Depends(get_current_user),
+    current_user: User = Depends(get_current_user_async),
     db: AsyncSession = Depends(get_db),
 ):
     """
@@ -173,7 +174,7 @@ async def get_image_library(
 @router.get("/{image_id}", response_model=ImageResponse)
 async def get_image(
     image_id: UUID,
-    current_user: User = Depends(get_current_user),
+    current_user: User = Depends(get_current_user_async),
     db: AsyncSession = Depends(get_db),
 ):
     """Get image by ID."""
@@ -193,7 +194,7 @@ async def get_image(
 @router.delete("/{image_id}", status_code=status.HTTP_204_NO_CONTENT)
 async def delete_image(
     image_id: UUID,
-    current_user: User = Depends(get_current_user),
+    current_user: User = Depends(get_current_user_async),
     db: AsyncSession = Depends(get_db),
 ):
     """
@@ -223,8 +224,8 @@ async def delete_image(
     from app.images.upload import delete_image_from_storage
 
     await delete_image_from_storage(image.storage_path)
-    if "thumbnails" in image.metadata:
-        await delete_thumbnails(image.metadata["thumbnails"])
+    if "thumbnails" in image.image_metadata:
+        await delete_thumbnails(image.image_metadata["thumbnails"])
 
     # Delete from database
     await repo.delete_image(image_id)
@@ -234,7 +235,7 @@ async def delete_image(
 async def add_image_to_board(
     board_id: UUID,
     data: BoardImageCreate,
-    current_user: User = Depends(get_current_user),
+    current_user: User = Depends(get_current_user_async),
     db: AsyncSession = Depends(get_db),
 ):
     """
@@ -243,8 +244,6 @@ async def add_image_to_board(
     The image must already be uploaded and owned by the current user.
     """
     # Verify board ownership
-    from sqlalchemy import select
-
     board_result = await db.execute(select(Board).where(Board.id == board_id))
     board = board_result.scalar_one_or_none()
 
@@ -284,7 +283,7 @@ async def update_board_image(
     board_id: UUID,
     image_id: UUID,
     data: BoardImageUpdate,
-    current_user: User = Depends(get_current_user),
+    current_user: User = Depends(get_current_user_async),
     db: AsyncSession = Depends(get_db),
 ):
     """
@@ -294,8 +293,6 @@ async def update_board_image(
     Only provided fields are updated.
     """
     # Verify board ownership
-    from sqlalchemy import select
-
     board_result = await db.execute(select(Board).where(Board.id == board_id))
     board = board_result.scalar_one_or_none()
 
@@ -329,7 +326,7 @@ async def update_board_image(
 async def remove_image_from_board(
     board_id: UUID,
     image_id: UUID,
-    current_user: User = Depends(get_current_user),
+    current_user: User = Depends(get_current_user_async),
     db: AsyncSession = Depends(get_db),
 ):
     """
@@ -339,8 +336,6 @@ async def remove_image_from_board(
     The image remains in the user's library.
     """
     # Verify board ownership
-    from sqlalchemy import select
-
     board_result = await db.execute(select(Board).where(Board.id == board_id))
     board = board_result.scalar_one_or_none()
 
@@ -362,7 +357,7 @@ async def remove_image_from_board(
 async def bulk_update_board_images(
     board_id: UUID,
     data: BulkImageUpdate,
-    current_user: User = Depends(get_current_user),
+    current_user: User = Depends(get_current_user_async),
     db: AsyncSession = Depends(get_db),
 ):
     """
@@ -371,8 +366,6 @@ async def bulk_update_board_images(
     Applies the same changes to all specified images. Useful for multi-selection operations.
     """
     # Verify board ownership
-    from sqlalchemy import select
-
     board_result = await db.execute(select(Board).where(Board.id == board_id))
     board = board_result.scalar_one_or_none()
 
@@ -438,7 +431,7 @@ async def bulk_update_board_images(
 @router.get("/boards/{board_id}/images", response_model=list[BoardImageResponse])
 async def get_board_images(
     board_id: UUID,
-    current_user: User = Depends(get_current_user),
+    current_user: User = Depends(get_current_user_async),
     db: AsyncSession = Depends(get_db),
 ):
     """
@@ -447,8 +440,6 @@ async def get_board_images(
     Used for loading board contents in the canvas.
     """
     # Verify board access (owner or shared link - for now just owner)
-    from sqlalchemy import select
-
     board_result = await db.execute(select(Board).where(Board.id == board_id))
     board = board_result.scalar_one_or_none()
 
diff --git a/backend/app/api/sharing.py b/backend/app/api/sharing.py
index ba15917..e0b7daa 100644
--- a/backend/app/api/sharing.py
+++ b/backend/app/api/sharing.py
@@ -1,6 +1,6 @@
 """Board sharing API endpoints."""
 
-from datetime import datetime
+from datetime import datetime, timezone
 from uuid import UUID
 
 from fastapi import APIRouter, Depends, HTTPException, status
@@ -54,7 +54,7 @@ def validate_share_link(token: str, db: Session, required_permission: str = "vie
         )
 
     # Check expiration
-    if share_link.expires_at and share_link.expires_at < datetime.utcnow():
+    if share_link.expires_at and share_link.expires_at < datetime.now(timezone.utc):
         raise HTTPException(
             status_code=status.HTTP_403_FORBIDDEN,
             detail="Share link has expired",
@@ -69,7 +69,7 @@ def validate_share_link(token: str, db: Session, required_permission: str = "vie
 
     # Update access tracking
     share_link.access_count += 1
-    share_link.last_accessed_at = datetime.utcnow()
+    share_link.last_accessed_at = datetime.now(timezone.utc)
     db.commit()
 
     return share_link
diff --git a/backend/app/auth/jwt.py b/backend/app/auth/jwt.py
index 6bd5411..6ebc1df 100644
--- a/backend/app/auth/jwt.py
+++ b/backend/app/auth/jwt.py
@@ -1,6 +1,6 @@
 """JWT token generation and validation."""
 
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from uuid import UUID
 
 from jose import JWTError, jwt
@@ -21,11 +21,11 @@ def create_access_token(user_id: UUID, email: str, expires_delta: timedelta | No
         Encoded JWT token string
     """
     if expires_delta:
-        expire = datetime.utcnow() + expires_delta
+        expire = datetime.now(timezone.utc) + expires_delta
     else:
-        expire = datetime.utcnow() + timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
+        expire = datetime.now(timezone.utc) + timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
 
-    to_encode = {"sub": str(user_id), "email": email, "exp": expire, "iat": datetime.utcnow(), "type": "access"}
+    to_encode = {"sub": str(user_id), "email": email, "exp": expire, "iat": datetime.now(timezone.utc), "type": "access"}
 
     encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
     return encoded_jwt
diff --git a/backend/app/boards/sharing.py b/backend/app/boards/sharing.py
index cbf1e81..f6fc621 100644
--- a/backend/app/boards/sharing.py
+++ b/backend/app/boards/sharing.py
@@ -2,7 +2,7 @@
 
 import secrets
 import string
-from datetime import datetime
+from datetime import datetime, timezone
 
 from sqlalchemy.orm import Session
 
@@ -53,12 +53,12 @@ def validate_share_link_token(token: str, db: Session) -> ShareLink | None:
         return None
 
     # Check expiration
-    if share_link.expires_at and share_link.expires_at < datetime.utcnow():
+    if share_link.expires_at and share_link.expires_at < datetime.now(timezone.utc):
         return None
 
     # Update access tracking
     share_link.access_count += 1
-    share_link.last_accessed_at = datetime.utcnow()
+    share_link.last_accessed_at = datetime.now(timezone.utc)
     db.commit()
 
     return share_link
diff --git a/backend/app/core/deps.py b/backend/app/core/deps.py
index 7e76934..04ef5ce 100644
--- a/backend/app/core/deps.py
+++ b/backend/app/core/deps.py
@@ -5,24 +5,50 @@ from uuid import UUID
 
 from fastapi import Depends, HTTPException, status
 from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.orm import Session
 
 from app.auth.jwt import decode_access_token
 from app.database.models.user import User
 from app.database.session import get_db
 
-# Database session dependency
-DatabaseSession = Annotated[Session, Depends(get_db)]
+# For backwards compatibility with synchronous code
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from app.core.config import settings
+
+# Sync engine for synchronous endpoints
+_sync_engine = create_engine(
+    str(settings.DATABASE_URL),
+    pool_size=settings.DATABASE_POOL_SIZE,
+    max_overflow=settings.DATABASE_MAX_OVERFLOW,
+    pool_pre_ping=True,
+)
+_SyncSessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=_sync_engine)
+
+
+def get_db_sync():
+    """Synchronous database session dependency."""
+    db = _SyncSessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+# Database session dependency (async)
+DatabaseSession = Annotated[AsyncSession, Depends(get_db)]
 
 # Security scheme for JWT Bearer token
 security = HTTPBearer()
 
 
 def get_current_user(
-    credentials: HTTPAuthorizationCredentials = Depends(security), db: Session = Depends(get_db)
+    credentials: HTTPAuthorizationCredentials = Depends(security), db: Session = Depends(get_db_sync)
 ) -> User:
     """
-    Get current authenticated user from JWT token.
+    Get current authenticated user from JWT token (synchronous version).
 
     Args:
         credentials: HTTP Authorization Bearer token
@@ -63,7 +89,7 @@ def get_current_user(
             headers={"WWW-Authenticate": "Bearer"},
         ) from None
 
-    # Get user from database
+    # Get user from database (sync)
     user = db.query(User).filter(User.id == user_id).first()
 
     if user is None:
@@ -77,3 +103,65 @@ def get_current_user(
         raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="User account is deactivated")
 
     return user
+
+
+async def get_current_user_async(
+    credentials: HTTPAuthorizationCredentials = Depends(security), db: AsyncSession = Depends(get_db)
+) -> User:
+    """
+    Get current authenticated user from JWT token (asynchronous version).
+
+    Args:
+        credentials: HTTP Authorization Bearer token
+        db: Async database session
+
+    Returns:
+        Current authenticated user
+
+    Raises:
+        HTTPException: If token is invalid or user not found
+    """
+    # Decode token
+    token = credentials.credentials
+    payload = decode_access_token(token)
+
+    if payload is None:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid authentication credentials",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+
+    # Extract user ID from token
+    user_id_str: str = payload.get("sub")
+    if user_id_str is None:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid token payload",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+
+    try:
+        user_id = UUID(user_id_str)
+    except ValueError:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid user ID in token",
+            headers={"WWW-Authenticate": "Bearer"},
+        ) from None
+
+    # Get user from database (async)
+    result = await db.execute(select(User).where(User.id == user_id))
+    user = result.scalar_one_or_none()
+
+    if user is None:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="User not found",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+
+    if not user.is_active:
+        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="User account is deactivated")
+
+    return user
diff --git a/backend/app/database/base.py b/backend/app/database/base.py
index 2118370..a1a389f 100644
--- a/backend/app/database/base.py
+++ b/backend/app/database/base.py
@@ -1,6 +1,6 @@
 """Base model for all database models."""
 
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Any
 from uuid import uuid4
 
@@ -22,7 +22,7 @@ class Base(DeclarativeBase):
 
     # Common columns for all models
     id: Any = Column(UUID(as_uuid=True), primary_key=True, default=uuid4)
-    created_at: Any = Column(DateTime, default=datetime.utcnow, nullable=False)
+    created_at: Any = Column(DateTime, default=lambda: datetime.now(timezone.utc), nullable=False)
 
     def dict(self) -> dict[str, Any]:
         """Convert model to dictionary."""
diff --git a/backend/app/database/models/board.py b/backend/app/database/models/board.py
index 0fac153..d393241 100644
--- a/backend/app/database/models/board.py
+++ b/backend/app/database/models/board.py
@@ -1,6 +1,6 @@
 """Board database model."""
 
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import TYPE_CHECKING
 from uuid import UUID, uuid4
 
@@ -42,9 +42,9 @@ class Board(Base):
         default=lambda: {"x": 0, "y": 0, "zoom": 1.0, "rotation": 0},
     )
 
-    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False, default=datetime.utcnow)
+    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
     updated_at: Mapped[datetime] = mapped_column(
-        DateTime, nullable=False, default=datetime.utcnow, onupdate=datetime.utcnow
+        DateTime, nullable=False, default=lambda: datetime.now(timezone.utc), onupdate=lambda: datetime.now(timezone.utc)
     )
     is_deleted: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
 
diff --git a/backend/app/database/models/board_image.py b/backend/app/database/models/board_image.py
index a996e83..70822b6 100644
--- a/backend/app/database/models/board_image.py
+++ b/backend/app/database/models/board_image.py
@@ -1,6 +1,6 @@
 """BoardImage database model - junction table for boards and images."""
 
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import TYPE_CHECKING
 from uuid import UUID, uuid4
 
@@ -52,9 +52,9 @@ class BoardImage(Base):
         PGUUID(as_uuid=True), ForeignKey("groups.id", ondelete="SET NULL"), nullable=True
     )
 
-    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False, default=datetime.utcnow)
+    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
     updated_at: Mapped[datetime] = mapped_column(
-        DateTime, nullable=False, default=datetime.utcnow, onupdate=datetime.utcnow
+        DateTime, nullable=False, default=lambda: datetime.now(timezone.utc), onupdate=lambda: datetime.now(timezone.utc)
     )
 
     # Relationships
diff --git a/backend/app/database/models/comment.py b/backend/app/database/models/comment.py
index e1b145e..715de5c 100644
--- a/backend/app/database/models/comment.py
+++ b/backend/app/database/models/comment.py
@@ -1,7 +1,7 @@
 """Comment model for board annotations."""
 
 import uuid
-from datetime import datetime
+from datetime import datetime, timezone
 
 from sqlalchemy import Boolean, Column, DateTime, ForeignKey, String, Text
 from sqlalchemy.dialects.postgresql import JSONB, UUID
@@ -21,7 +21,7 @@ class Comment(Base):
     author_name = Column(String(100), nullable=False)
     content = Column(Text, nullable=False)
     position = Column(JSONB, nullable=True)  # Optional canvas position reference
-    created_at = Column(DateTime, nullable=False, default=datetime.utcnow)
+    created_at = Column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
     is_deleted = Column(Boolean, nullable=False, default=False)
 
     # Relationships
diff --git a/backend/app/database/models/group.py b/backend/app/database/models/group.py
index fced044..034fd7d 100644
--- a/backend/app/database/models/group.py
+++ b/backend/app/database/models/group.py
@@ -1,6 +1,6 @@
 """Group database model."""
 
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import TYPE_CHECKING
 from uuid import UUID, uuid4
 
@@ -33,9 +33,9 @@ class Group(Base):
     color: Mapped[str] = mapped_column(String(7), nullable=False)  # Hex color #RRGGBB
     annotation: Mapped[str | None] = mapped_column(Text, nullable=True)
 
-    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False, default=datetime.utcnow)
+    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
     updated_at: Mapped[datetime] = mapped_column(
-        DateTime, nullable=False, default=datetime.utcnow, onupdate=datetime.utcnow
+        DateTime, nullable=False, default=lambda: datetime.now(timezone.utc), onupdate=lambda: datetime.now(timezone.utc)
     )
 
     # Relationships
diff --git a/backend/app/database/models/image.py b/backend/app/database/models/image.py
index 5bfa442..7e9d5f9 100644
--- a/backend/app/database/models/image.py
+++ b/backend/app/database/models/image.py
@@ -1,6 +1,6 @@
 """Image database model."""
 
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import TYPE_CHECKING
 from uuid import UUID, uuid4
 
@@ -38,7 +38,7 @@ class Image(Base):
     height: Mapped[int] = mapped_column(Integer, nullable=False)
     image_metadata: Mapped[dict] = mapped_column(JSONB, nullable=False)
 
-    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False, default=datetime.utcnow)
+    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
     reference_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
 
     # Relationships
diff --git a/backend/app/database/models/share_link.py b/backend/app/database/models/share_link.py
index 34ada78..5dd0a45 100644
--- a/backend/app/database/models/share_link.py
+++ b/backend/app/database/models/share_link.py
@@ -1,7 +1,7 @@
 """ShareLink model for board sharing functionality."""
 
 import uuid
-from datetime import datetime
+from datetime import datetime, timezone
 
 from sqlalchemy import Boolean, Column, DateTime, ForeignKey, Integer, String
 from sqlalchemy.dialects.postgresql import UUID
@@ -19,7 +19,7 @@ class ShareLink(Base):
     board_id = Column(UUID(as_uuid=True), ForeignKey("boards.id", ondelete="CASCADE"), nullable=False)
     token = Column(String(64), unique=True, nullable=False, index=True)
     permission_level = Column(String(20), nullable=False)  # 'view-only' or 'view-comment'
-    created_at = Column(DateTime, nullable=False, default=datetime.utcnow)
+    created_at = Column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
     expires_at = Column(DateTime, nullable=True)
     last_accessed_at = Column(DateTime, nullable=True)
     access_count = Column(Integer, nullable=False, default=0)
diff --git a/backend/app/database/models/user.py b/backend/app/database/models/user.py
index ebfec48..c76efed 100644
--- a/backend/app/database/models/user.py
+++ b/backend/app/database/models/user.py
@@ -1,7 +1,7 @@
 """User model for authentication and ownership."""
 
 import uuid
-from datetime import datetime
+from datetime import datetime, timezone
 
 from sqlalchemy import Boolean, Column, DateTime, String
 from sqlalchemy.dialects.postgresql import UUID
@@ -18,8 +18,8 @@ class User(Base):
     id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
     email = Column(String(255), unique=True, nullable=False, index=True)
     password_hash = Column(String(255), nullable=False)
-    created_at = Column(DateTime, nullable=False, default=datetime.utcnow)
-    updated_at = Column(DateTime, nullable=False, default=datetime.utcnow, onupdate=datetime.utcnow)
+    created_at = Column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
+    updated_at = Column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc), onupdate=lambda: datetime.now(timezone.utc))
     is_active = Column(Boolean, nullable=False, default=True)
 
     # Relationships
diff --git a/backend/app/database/session.py b/backend/app/database/session.py
index cb299d6..85bb8b6 100644
--- a/backend/app/database/session.py
+++ b/backend/app/database/session.py
@@ -1,27 +1,33 @@
 """Database session management."""
 
-from sqlalchemy import create_engine
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
 from sqlalchemy.orm import sessionmaker
 
 from app.core.config import settings
 
-# Create SQLAlchemy engine
-engine = create_engine(
-    str(settings.DATABASE_URL),
+# Convert sync DATABASE_URL to async (replace postgresql:// with postgresql+asyncpg://)
+async_database_url = str(settings.DATABASE_URL).replace("postgresql://", "postgresql+asyncpg://")
+
+# Create async SQLAlchemy engine
+engine = create_async_engine(
+    async_database_url,
     pool_size=settings.DATABASE_POOL_SIZE,
     max_overflow=settings.DATABASE_MAX_OVERFLOW,
     pool_pre_ping=True,  # Verify connections before using
     echo=settings.DEBUG,  # Log SQL queries in debug mode
 )
 
-# Create session factory
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+# Create async session factory
+SessionLocal = sessionmaker(
+    bind=engine,
+    class_=AsyncSession,
+    autocommit=False,
+    autoflush=False,
+    expire_on_commit=False,
+)
 
 
-def get_db():
-    """Dependency for getting database session."""
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
+async def get_db():
+    """Dependency for getting async database session."""
+    async with SessionLocal() as session:
+        yield session
diff --git a/backend/app/images/repository.py b/backend/app/images/repository.py
index 14b321e..f7c5b40 100644
--- a/backend/app/images/repository.py
+++ b/backend/app/images/repository.py
@@ -3,7 +3,8 @@
 from collections.abc import Sequence
 from uuid import UUID
 
-from sqlalchemy.orm import Session
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.database.models.board_image import BoardImage
 from app.database.models.image import Image
@@ -12,11 +13,11 @@ from app.database.models.image import Image
 class ImageRepository:
     """Repository for image database operations."""
 
-    def __init__(self, db: Session):
+    def __init__(self, db: AsyncSession):
         """Initialize repository with database session."""
         self.db = db
 
-    def create_image(
+    async def create_image(
         self,
         user_id: UUID,
         filename: str,
@@ -25,7 +26,7 @@ class ImageRepository:
         mime_type: str,
         width: int,
         height: int,
-        metadata: dict,
+        image_metadata: dict,
     ) -> Image:
         """Create new image record."""
         image = Image(
@@ -36,59 +37,68 @@ class ImageRepository:
             mime_type=mime_type,
             width=width,
             height=height,
-            image_metadata=metadata,
+            image_metadata=image_metadata,
         )
         self.db.add(image)
-        self.db.commit()
-        self.db.refresh(image)
+        await self.db.commit()
+        await self.db.refresh(image)
         return image
 
-    def get_image_by_id(self, image_id: UUID) -> Image | None:
+    async def get_image_by_id(self, image_id: UUID) -> Image | None:
         """Get image by ID."""
-        return self.db.query(Image).filter(Image.id == image_id).first()
+        result = await self.db.execute(select(Image).where(Image.id == image_id))
+        return result.scalar_one_or_none()
 
-    def get_user_images(
+    async def get_user_images(
         self, user_id: UUID, limit: int = 50, offset: int = 0
     ) -> tuple[Sequence[Image], int]:
         """Get all images for a user with pagination."""
-        total = self.db.query(Image).filter(Image.user_id == user_id).count()
-        images = (
-            self.db.query(Image)
-            .filter(Image.user_id == user_id)
+        from sqlalchemy import func
+        
+        # Get total count efficiently
+        count_result = await self.db.execute(
+            select(func.count(Image.id)).where(Image.user_id == user_id)
+        )
+        total = count_result.scalar_one()
+        
+        # Get paginated images
+        result = await self.db.execute(
+            select(Image)
+            .where(Image.user_id == user_id)
             .order_by(Image.created_at.desc())
             .limit(limit)
             .offset(offset)
-            .all()
         )
+        images = result.scalars().all()
         return images, total
 
-    def delete_image(self, image_id: UUID) -> bool:
+    async def delete_image(self, image_id: UUID) -> bool:
         """Delete image record."""
-        image = self.get_image_by_id(image_id)
+        image = await self.get_image_by_id(image_id)
         if not image:
             return False
 
-        self.db.delete(image)
-        self.db.commit()
+        await self.db.delete(image)
+        await self.db.commit()
         return True
 
-    def increment_reference_count(self, image_id: UUID) -> None:
+    async def increment_reference_count(self, image_id: UUID) -> None:
         """Increment reference count for image."""
-        image = self.get_image_by_id(image_id)
+        image = await self.get_image_by_id(image_id)
         if image:
             image.reference_count += 1
-            self.db.commit()
+            await self.db.commit()
 
-    def decrement_reference_count(self, image_id: UUID) -> int:
+    async def decrement_reference_count(self, image_id: UUID) -> int:
         """Decrement reference count for image."""
-        image = self.get_image_by_id(image_id)
+        image = await self.get_image_by_id(image_id)
         if image and image.reference_count > 0:
             image.reference_count -= 1
-            self.db.commit()
+            await self.db.commit()
             return image.reference_count
         return 0
 
-    def add_image_to_board(
+    async def add_image_to_board(
         self,
         board_id: UUID,
         image_id: UUID,
@@ -107,36 +117,68 @@ class ImageRepository:
         self.db.add(board_image)
 
         # Increment reference count
-        self.increment_reference_count(image_id)
+        await self.increment_reference_count(image_id)
 
-        self.db.commit()
-        self.db.refresh(board_image)
+        await self.db.commit()
+        await self.db.refresh(board_image)
         return board_image
 
-    def get_board_images(self, board_id: UUID) -> Sequence[BoardImage]:
+    async def get_board_images(self, board_id: UUID) -> Sequence[BoardImage]:
         """Get all images for a board, ordered by z-order."""
-        return (
-            self.db.query(BoardImage)
-            .filter(BoardImage.board_id == board_id)
+        result = await self.db.execute(
+            select(BoardImage)
+            .where(BoardImage.board_id == board_id)
             .order_by(BoardImage.z_order.asc())
-            .all()
         )
+        return result.scalars().all()
 
-    def remove_image_from_board(self, board_id: UUID, image_id: UUID) -> bool:
-        """Remove image from board."""
-        board_image = (
-            self.db.query(BoardImage)
-            .filter(BoardImage.board_id == board_id, BoardImage.image_id == image_id)
-            .first()
+    async def get_board_image(self, board_id: UUID, image_id: UUID) -> BoardImage | None:
+        """Get a specific board image."""
+        result = await self.db.execute(
+            select(BoardImage)
+            .where(BoardImage.board_id == board_id, BoardImage.image_id == image_id)
         )
+        return result.scalar_one_or_none()
+
+    async def update_board_image(
+        self,
+        board_id: UUID,
+        image_id: UUID,
+        position: dict | None = None,
+        transformations: dict | None = None,
+        z_order: int | None = None,
+        group_id: UUID | None = None,
+    ) -> BoardImage | None:
+        """Update board image position, transformations, z-order, or group."""
+        board_image = await self.get_board_image(board_id, image_id)
+        
+        if not board_image:
+            return None
+
+        if position is not None:
+            board_image.position = position
+        if transformations is not None:
+            board_image.transformations = transformations
+        if z_order is not None:
+            board_image.z_order = z_order
+        if group_id is not None:
+            board_image.group_id = group_id
+
+        await self.db.commit()
+        await self.db.refresh(board_image)
+        return board_image
+
+    async def remove_image_from_board(self, board_id: UUID, image_id: UUID) -> bool:
+        """Remove image from board."""
+        board_image = await self.get_board_image(board_id, image_id)
 
         if not board_image:
             return False
 
-        self.db.delete(board_image)
+        await self.db.delete(board_image)
 
         # Decrement reference count
-        self.decrement_reference_count(image_id)
+        await self.decrement_reference_count(image_id)
 
-        self.db.commit()
+        await self.db.commit()
         return True
diff --git a/backend/app/images/schemas.py b/backend/app/images/schemas.py
index dfa12c3..bb91e35 100644
--- a/backend/app/images/schemas.py
+++ b/backend/app/images/schemas.py
@@ -26,13 +26,14 @@ class ImageUploadResponse(BaseModel):
     mime_type: str
     width: int
     height: int
-    metadata: dict[str, Any]
+    metadata: dict[str, Any] = Field(..., alias="image_metadata")
     created_at: datetime
 
     class Config:
         """Pydantic config."""
 
         from_attributes = True
+        populate_by_name = True
 
 
 class ImageResponse(BaseModel):
@@ -46,7 +47,7 @@ class ImageResponse(BaseModel):
     mime_type: str
     width: int
     height: int
-    metadata: dict[str, Any]
+    metadata: dict[str, Any] = Field(..., alias="image_metadata")
     created_at: datetime
     reference_count: int
 
@@ -54,6 +55,7 @@ class ImageResponse(BaseModel):
         """Pydantic config."""
 
         from_attributes = True
+        populate_by_name = True
 
 
 class BoardImageCreate(BaseModel):
diff --git a/flake.nix b/flake.nix
index 10809a2..4b1c4a2 100644
--- a/flake.nix
+++ b/flake.nix
@@ -31,7 +31,8 @@
           alembic
           pydantic
           pydantic-settings # Settings management
-          psycopg2 # PostgreSQL driver
+          psycopg2 # PostgreSQL driver (sync)
+          asyncpg # PostgreSQL driver (async)
           # Auth & Security
           python-jose
           passlib
@@ -88,6 +89,7 @@
           # Development tools
           git
           direnv
+          tmux
         ];
 
         shellHook = ''
@@ -105,6 +107,7 @@
           echo "   Status:     ./scripts/dev-services.sh status"
           echo ""
           echo "📚 Quick Commands:"
+          echo "   Dev (tmux): nix run .#dev"
           echo "   Backend:    cd backend && uvicorn app.main:app --reload"
           echo "   Frontend:   cd frontend && npm run dev"
           echo "   Database:   psql -h localhost -U webref webref"
@@ -131,6 +134,7 @@
           type = "app";
           program = "${pkgs.writeShellScript "help" ''
             echo "Available commands:"
+            echo "  nix run .#dev           - Start backend + frontend in tmux"
             echo "  nix run .#lint          - Run all linting checks"
             echo "  nix run .#lint-backend  - Run backend linting only"
             echo "  nix run .#lint-frontend - Run frontend linting only"
@@ -138,6 +142,76 @@
           ''}";
         };
 
+        # Development runner with tmux
+        dev = {
+          type = "app";
+          program = "${pkgs.writeShellScript "dev-tmux" ''
+            set -e
+
+            # Check if we're in the project root
+            if [ ! -d "backend" ] || [ ! -d "frontend" ]; then
+              echo "❌ Error: Not in project root directory"
+              echo "Please run this command from the webref project root"
+              exit 1
+            fi
+
+            # Check if frontend dependencies are installed
+            if [ ! -d "frontend/node_modules" ]; then
+              echo "📦 Installing frontend dependencies..."
+              cd frontend
+              ${pkgs.nodejs}/bin/npm install
+              cd ..
+            fi
+
+            # Set environment variables
+            export DATABASE_URL="postgresql://webref@localhost:5432/webref"
+            export MINIO_ENDPOINT="localhost:9000"
+            export MINIO_ACCESS_KEY="minioadmin"
+            export MINIO_SECRET_KEY="minioadmin"
+            export PYTHONPATH="$PWD/backend:$PYTHONPATH"
+            export PATH="${pythonEnv}/bin:${pkgs.nodejs}/bin:$PATH"
+
+            # Session name
+            SESSION_NAME="webref-dev"
+
+            # Kill existing session if it exists
+            ${pkgs.tmux}/bin/tmux has-session -t $SESSION_NAME 2>/dev/null && ${pkgs.tmux}/bin/tmux kill-session -t $SESSION_NAME
+
+            echo "🚀 Starting development environment in tmux..."
+            echo ""
+            echo "📋 Tmux Controls:"
+            echo "   Switch panes:    Ctrl+b → arrow keys"
+            echo "   Scroll mode:     Ctrl+b → ["
+            echo "   Exit scroll:     q"
+            echo "   Detach session:  Ctrl+b → d"
+            echo "   Kill session:    Ctrl+b → :kill-session"
+            echo ""
+            echo "Starting in 2 seconds..."
+            sleep 2
+
+            # Create new tmux session with backend
+            ${pkgs.tmux}/bin/tmux new-session -d -s "$SESSION_NAME" -n "webref" -c "$PWD/backend" \
+              "printf '\n🐍 Starting Backend (uvicorn)...\n\n' && ${pythonEnv}/bin/uvicorn app.main:app --reload --host 0.0.0.0 --port 8000; read -p 'Backend stopped. Press Enter to exit...'"
+
+            # Split window vertically and run frontend
+            ${pkgs.tmux}/bin/tmux split-window -h -t "$SESSION_NAME":0 -c "$PWD/frontend" \
+              "printf '\n⚡ Starting Frontend (Vite)...\n\n' && ${pkgs.nodejs}/bin/npm run dev; read -p 'Frontend stopped. Press Enter to exit...'"
+
+            # Set pane titles
+            ${pkgs.tmux}/bin/tmux select-pane -t "$SESSION_NAME":0.0 -T "Backend (uvicorn)"
+            ${pkgs.tmux}/bin/tmux select-pane -t "$SESSION_NAME":0.1 -T "Frontend (vite)"
+
+            # Balance panes
+            ${pkgs.tmux}/bin/tmux select-layout -t "$SESSION_NAME":0 even-horizontal
+
+            # Focus on backend pane
+            ${pkgs.tmux}/bin/tmux select-pane -t "$SESSION_NAME":0.0
+
+            # Attach to session
+            ${pkgs.tmux}/bin/tmux attach-session -t "$SESSION_NAME"
+          ''}";
+        };
+
         # Unified linting - calls both backend and frontend lints
         lint = {
           type = "app";