Manage Request-Scoped Resources in FastAPI with Depends
Use FastAPI Depends with generator dependencies to manage database sessions and auth per request, then override them in tests without changing route code.
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pythonFastAPI Lifespan and app.state: Managing Process-Wide Resources
Use FastAPI's lifespan context manager to create and dispose shared clients or pools once at startup and shutdown, expose them via app.state, and keep request-scoped cleanup in dependencies with yield.
Diagnosing 422 Validation Failures in FastAPI Async Endpoints
When a FastAPI async endpoint returns 422 on seemingly valid data, the fault usually lies in the Pydantic model, dependency signature, or request Content-Type—not the endpoint logic.
FastAPI Resource Management: Choosing Lifespan over on_event
Learn why the FastAPI lifespan context manager is the preferred choice over deprecated on_event handlers for managing async startup and shutdown resources.
Managing Request State with FastAPI Dependency Injection
Learn how to use FastAPI's Dependency Injection system to manage database sessions and request state without leaking resources or duplicating code.
sqlalchemyUsing FastAPI Dependency Injection for Safe Resource Management
Learn how FastAPI's Depends and yield patterns eliminate duplicated setup code and guarantee cleanup of database sessions, auth tokens, and other shared resources.
FastAPI Off-Loading: Background Tasks vs Async Endpoints vs External Queues
Decide when to use FastAPI BackgroundTasks, async endpoints, or an external queue. Compare complexity, reliability, and latency, then implement a 202 Accepted off-load pattern with validation.
Decoupling FastAPI Logic with Dependency Injection
Stop writing 'fat' route handlers in FastAPI. Learn how to use Dependency Injection to decouple resource creation from business logic for cleaner, testable code.
FastAPI Dependency Injection Failures: A Diagnostic Guide
A diagnostic guide to FastAPI dependency injection failures: how to spot a missing Depends marker, a called dependency, leaked test overrides, and blocking async dependencies.