The GIL means you only get to use a single core for your code that's written in Python, but that limit doesn't hold for parts that use C extensions which release the GIL - and there are a lot of those.

The GIL is also on the way out: Python 3.13 already shipped the first builds of "free threading" Python and 3.14 and onwards will continue to make progress on that front: https://docs.python.org/3/howto/free-threading-python.html

And honestly, a Python web app running on a single core is still likely good for hundreds or even thousands of requests a second. The vast majority of web apps get a fraction of that.

I’ve been running essential production systems with pythons uvicorn and 1 worker reliably, mainly because I get to use global state and the performance is more than fine. It’s much better than having to store global state somewhere else. Just make sure you measure the usage and chose a different design when you notice when this becomes a problem.