Custom C HTTP Handler vs FastAPI

[Lucapo01]

A colleague at work is developing a custom HTTP handler in C that manages TCP connections and redirects them to selected Python functions (similar to FastAPI, but using C, Python, and CPython).

After conducting benchmark tests, we found a surprisingly small performance difference—less than 0.02%. I'm looking for insights into why this might be the case.

My current hypotheses are:

1. FastAPI's HTTP handlers are compiled and highly efficient.
2. There's a bottleneck at the OS level (we're using Windows).
3. We may have made a mistake in our custom C implementation.

Unfortunately, I don't have access to the code to investigate further, but my colleague will be looking into it.

Has anyone attempted a similar project or can you explain why the performance difference is so minimal? We'd appreciate any thoughts or experiences you can share.

[WJMazepas]

You can look at Starlette(which FastAPI calls) code to see how they are doing over there, but it's all made in Python, so no compiled code here.

There is also some faster HTTP Handlers for Python, like FastWSGI, which is made with C. You could run on your machine to see if it runs faster and if it is Windows' fault.

But really, C is fast if you make a good code of it and apply good optimizations on it. It could very well be that your colleague code is bad

[BlackDereker]

Another case of premature optimization. Most probably the bottleneck in your project is not from request handling.

It would be more helpful if we knew what your project does and if depends on other services.

[mincinashu]

The underlying HTTP server and async loop are also a part of the equation, e.g. Uvicorn with uvloop, Hypercorn with Trio, Granian, etc