I'm saying there are very few real black and whites, and everything in life and in software is more kind of grey. As such there are very few black and white ru

I'm saying there are very few real black and whites, and everything in life and in software is more kind of grey. As such there are very few black and white rules you can follow and succeed. The correct approach is somewhere to the left of "premature optimization" and somewhere to the right of "don't even think about performance until you can measure it". More experienced and talented people will be more successful at picking that sweet spot. Telling a dev that the correct approach is to pay absolutely no attention to performance before it can be measured is ... crazy IMO. I would expect them to have at least thought about it, and have some opinions, just as they should not have put excessive effort into prematurely optimizing things they don't know are going to be a problem. My point is - its grey, use your brains, don't buy into absolute rules.