Speed up FastAPI startup by caching its dependency-tree introspection.

At startup, FastAPI re-introspects every route's dependency tree with no caching, so dependencies shared across many routes (auth checks, DB handles, role guards …) are parsed from scratch again and again. fastapi-cache-di memoizes that work for the duration of route loading, turning O(routes × tree-depth) into O(routes + unique-deps), then restores FastAPI's originals.

pip install fastapi-cache-di
# or
uv add fastapi-cache-di

Wrap the code that loads your routes with the context manager:

from fastapi import APIRouter, FastAPI

from fastapi_cache_di import fastapi_deps_cache

app = FastAPI()
users = APIRouter()
orders = APIRouter()
billing = APIRouter()

with fastapi_deps_cache():
    # Registering routes introspects each dependency tree; caching is active here.
    app.include_router(users)
    app.include_router(orders)
    app.include_router(billing)
# originals restored here; cache memory freed

Manual patch/unpatch, sharing and inspecting the cache, and the cache-key details are covered in the documentation.

Full documentation is available at toilal.github.io/fastapi-cache-di (usage guide, internals, and API reference).

• Python ≥ 3.12
• FastAPI ≥ 0.112.4

MIT © Rémi Alvergnat