200ms -> 100ms for a whole request (not just a tiny part of a request) is indeed worthwhile, I never meant to disagree with that. But for micro-optimisations, y

200ms -> 100ms for a whole request (not just a tiny part of a request) is indeed worthwhile, I never meant to disagree with that. But for micro-optimisations, you'd be lucky to get a 10% speed increase in 10% of things you do, which would only give only a speed increase of 1% overall (obviously those are made up numbers to illustrate the idea). As I said in my first comment, usually the actual gains come from using a different data structures or making vectorised calls in to C libraries, and I assume that's what you mean by the effective refactorings in your case.