One of the things I had to wrap my head around was the whole async server style of programming. I learned that doing a sleep on the server consumes essentially zero resources. The thread goes to sleep and wakes up when the timer expires. In the meantime the server can handle other requests unhindered. You can have hundreds or thousands of these threads at the same time - serving requests, waiting for IO, etc.

It’s not like synchronous servers e.g. Flask with Gunicorn (in the Python world) where you have a few pre-forked server processes. In that case it would be a waste to prevent one of those processes from serving other requests while sleeping, I agree.

Ultimately it’s cool though to be able to control the client from the backend asynchronously, updating signals (think of them as a kind of special front-end variable with superpowers) when something on the backend happens, or updating the client’s DOM, or running scripts.