Skip to content

Architecture

Modern Django exposes both WSGI and ASGI entrypoints. FastAPI is ASGI-only. This bridge composes a FastAPI application and Django's ASGI application under one outer Starlette router.

                    ┌──────────────────────────┐
HTTP request ──────▶│ combined ASGI application│
                    └────────────┬─────────────┘
                                 │
                    ┌────────────┴─────────────┐
                    │                          │
             matches PREFIX              no prefix match
                    │                          │
                    ▼                          ▼
                FastAPI                   Django ASGI

Django must be initialized before application routers import Django models. get_django_fastapi_application() calls Django's normal get_asgi_application() first and then creates and mounts FastAPI.

Shared process state

When both applications run in one ASGI process they naturally share:

  • DJANGO_SETTINGS_MODULE and Django settings;
  • database connections and model definitions;
  • cache and session configuration;
  • authentication backends;
  • environment variables and logging configuration.

When WSGI and ASGI run as separate services, they still share those logical resources, but each service has its own processes and connection pools. See the WSGI deployment guide.

Request adaptation

get_django_request builds a Django ASGIRequest from the FastAPI request, attaches Django's session, resolves a user, and caches the result on request.state. This is an adapter, not a pass through Django's configured middleware chain.

The default authentication resolver runs Django's AuthenticationMiddleware. Unsafe methods also run Django's CsrfViewMiddleware unless exempted.

Sync and async are endpoint decisions

The server protocol does not make every function asynchronous:

  • FastAPI runs def operations in a worker thread. Normal synchronous Django ORM calls are appropriate there.
  • FastAPI runs async def operations in the event loop. Use Django's async ORM methods or cross to one synchronous service with sync_to_async.