In mobile development, the bar is pretty clear: your app should not drop frames, never hang on the UI thread, and interactions should not take longer than the u

In mobile development, the bar is pretty clear: your app should not drop frames, never hang on the UI thread, and interactions should not take longer than the user-perceptible 100ms. The silicon is N years old and it can't scale horizontally, so either the user has a fluid experience using your app or they don't. How do backend developers determine what is and is not reasonable performance for a given service? I see so many stories from companies of "we switched to the right tool for the job and saved so many CPU cycles!". From the outside it sounds like half of the problem is determining you have a problem in the first place.