that largely depends on your machine's specs but the limit is much higher that you are going to get in go, python or ruby (yes I know action cable uses go)

but to get a better handle, here's some interesting reading

https://www.phoenixframework.org/blog/the-road-to-2-million-...

https://expertise.jetruby.com/websockets-how-to-rails-action...

I could tell you the result but the difference is so stark, you might think I'm exaggerating