Production FastAPI

This skill encodes battle-tested patterns for shipping FastAPI applications that survive real production traffic. Every recommendation here comes from outage post-mortems, not blog posts. The patterns are opinionated — this is a senior engineer review, not a tutorial.

See templates/ for copy-paste-ready implementations of every pattern below.

1. Application Lifecycle

Use lifespan, not on_event. The on_event decorator is deprecated and does not support shared state between startup and shutdown.

from contextlib import asynccontextmanager
from fastapi import FastAPI
import httpx
from sqlalchemy.ext.asyncio import create_async_engine