ReadMeFeed / Community knowledge
Real questions. Useful conversations. Find the people who know your stack.
Frameworks & web · #fastapi
Guide comparing Pydantic models vs. plain dict request bodies in FastAPI, with a decision table, trade‑offs, and a working example.
Learn how FastAPI caches dependencies per request, shares sub‑dependency instances, and lets you swap them in tests without touching production data.
Compare FastAPI's lifespan context manager with legacy on_event hooks. Learn how to safely initialize DB pools and shared resources using app.state for better testability and ASGI compliance.
Learn how to diagnose and fix 422 Unprocessable Entity errors in FastAPI by analyzing Pydantic validation failures, request headers, and schema mismatches.
Stop leaking database connections in FastAPI. Learn how to use 'yield' dependencies to automate session setup and teardown for every request.
In a local development environment, a FastAPI dependency can be overridden using app.dependency_overrides[SomeDependency] = lambda: mock_service to inject a test double. When the same application is built as a Docker image and run in production, the override appears to be ignored and the real dependency is used instead. The service is launched with Uvicorn v
python
sqlalchemy
docker