+1 for py-spy. I would love to try out Scalene but the application I have does something funky with pickling for multiprocessing, breaking Scalene in the process (my fault, not Scalene's, I'll be looking into that). Py-spy worked, including catching all the sub-processes. Feeding the py-spy JSON output into https://speedscope.app makes for a very easy way to profile in a time crunch if you don't have time to get familiar with CLI tools or can't install stuff locally but have a browser and internet connection.

>where people told me there were network problems but it was actually not

Always ask if they assume it's network bound or they have measurements. Measurements may sometimes be wrong, but assumptions are more often wrong than right in performance engineering.

kudos for actually looking what the problem is.

As a (former) NetEng, it bothers me to no end that so many people claim "it's the network" when their application is slow / broken, without understanding the actual problem.