fastapi-advanced

Manage async database sessions per request in FastAPI by using typed dependency injection to provide an AsyncSession that opens and closes automatically for each route handler invocation. This ensures resources are properly released without duplicated cleanup code.

Structure FastAPI error handling by creating a custom AppError system and registering centralized exception handlers to format consistent JSON error responses across all endpoints. This prevents fragile error semantics and duplicated try-catch blocks in route handlers.

Implement authenticated FastAPI dependencies by chaining typed dependencies to extract the current user and enforce role checks, securing admin-only routes without cluttering route handler logic. This keeps access control logic reusable across multiple endpoints.

Use FastAPI background tasks for fire-and-forget operations like notifications and nonblocking workflows within the same process, but switch to an external job queue for heavy or durable processing requirements. Background tasks run after the response is sent without blocking the client.

Add request timing and logging middleware to a FastAPI application by defining middleware components that intercept requests to record processing duration and attach timing headers to responses. This provides observability into API performance without modifying individual endpoints.

Use WebSockets with FastAPI dependency injection by applying the same typed dependency patterns for database sessions and authentication to WebSocket endpoints, ensuring consistent resource lifecycle management. This allows real-time communication endpoints to share security and session logic with REST routes.