I don't think this is true. There are a lot of applications and services that I avoid because they are so slow that they are painful. I don't think you should be worrying about ensuring that your API is always <10ms but good general performance patterns (especially considering the scaling as you write code, limit yourself to O(n) unless you can be very sure that `n` will always be small) can keep you within interactive performance without needing to worry too much about it.