FastAPI + async Python: Patterns I Use Every Day

Why FastAPI

Type hints double as validation. OpenAPI docs come for free. For ML backends that expose models, it is a sweet spot.

Async carefully

Not every library is async-safe. Sometimes a thread pool around blocking code is the honest fix.

Structure

Keep routers thin, services testable, and settings in one place. Your future self will thank you.

One rule

Return explicit error shapes in production so clients can handle failures without guessing.