"Focus on making a product people wanna actually use first. If you're lucky enough to get to scale you can work about optimizing it then." This seems like a fa

"Focus on making a product people wanna actually use first. If you're lucky enough to get to scale you can work about optimizing it then." This seems like a false dichotomy. Avoiding obvious performance mistakes such as the ones you mentioned does not require additional focus that would detract from general building. It just requires that you know what you are doing. If you are the type of person who makes said mistakes, its unlikely you would ever go back and fix them by "focusing" on performance because the issue is simply that you don't know what you don't know. Likely someone else will come along in future and point out your mistakes to you. Optimization that actually hinders you from building and requires focus is at the very margins and almost no one is going to those levels in typical "application" code.