2026Systems
slowfw
SlowAPI: one Python handler, served over WSGI and ASGI.
A Python web framework that is a WSGI application and an ASGI application at the same time. Express ergonomics, FastAPI typing and NestJS structure, with zero required runtime dependencies. Write the handler that fits the work and pick the server later.
How it works
1
No sync-vs-async lock-in
The same file runs under gunicorn and uvicorn. Sync handlers work on ASGI, async handlers work on WSGI, with no shim or rewrite.
2
Picks the cheapest path per route
At registration it checks whether a route's whole chain (middleware, guards, pipes, dependencies) is synchronous. A fully sync WSGI request never creates an event loop.
3
One long-lived loop per process
Async connection pools and locks survive across requests on a gunicorn worker, instead of an asyncio.run per request.
Built with
Python
WSGI
ASGI
OpenAPI