AioHTTP vs FastAPI: When to Choose Which

I've shipped production services with both AioHTTP and FastAPI. They're often compared, but the real question isn't "which is better" — it's "which fits your situation."

AioHTTP: raw power, full control

AioHTTP gives you a low-level HTTP server and client. There's no magic. You wire up routes manually, handle request parsing yourself, and choose every dependency. This means:

• Excellent for services where you need tight control over the request lifecycle
• Great when you're building something that doesn't fit the typical REST CRUD pattern
• No automatic validation — you write it or bring your own library

FastAPI: productivity and standards

FastAPI is built on Starlette and Pydantic. It gives you automatic request validation, OpenAPI docs out of the box, and a clean dependency injection system. The tradeoff:

• Pydantic adds overhead — measurable on very high-throughput endpoints
• The "magic" of automatic validation can hide bugs if you don't understand what's happening
• Excellent for teams and APIs consumed by other developers

My rule of thumb

If the service has a public API or a team consuming it — use FastAPI. The automatic docs and validation save more time than they cost.

If the service is internal, performance-critical, or has unusual requirements (WebSocket-heavy, custom protocols, streaming) — AioHTTP gives you more room to breathe.

The best framework is the one your team can debug at 2am without reading the docs.