What happens when an HTTP request reaches FastAPI?
A single GET request crosses a socket, an ASGI server, a router, a dependency graph, and a serializer. Here is what each layer does, and where it can fail.
Topics
#architecture
3 articles
How FastAPI resolves a dependency
One Depends parameter can hide a tree of sub-dependencies, per-request cache entries, and cleanup code. Follow the solve order and see where request-scoped resources begin and end.
Connection pools are a latency budget
A pool limits concurrency. Past that limit, requests queue, and the wait never appears in database metrics. Here is how to size the pool from a request deadline instead of a guess.