Which is the fastest ASGI server?

ASGI is a specification which allows interoperability of async Python web frameworks and servers. There are several different ASGI servers (Daphne, Hypercorn, Uvicorn).

I was recently doing some load testing for a website, which has to support large numbers of visitors concurrently. I didn't expect there to be any dramatic differences in performance between the different ASGI servers, but even if there's a 20% difference, I'll take it.

It's also a good opportunity to show off Locust, which is a nice load testing tool.

The testing process and results are documented on GitHub.

Results

Uvicorn:

Hypercorn:

Daphne:

Conclusions

Uvicorn achieved roughly 40% more throughput than the others in this test. However, they all did well, and were stable under high load.