> But IMO the big-O/performance part should really mostly just be done on a by-need basis I agree >(i.e. you've identified your bottleneck and determined its

> But IMO the big-O/performance part should really mostly just be done on a by-need basis I agree >(i.e. you've identified your bottleneck and determined its worth the time to improve it). For this, though, it is often possible to identify this BEFORE writing any code. As opposed to refactoring an inner loop, Big-O challenges may often stem from (at least in my experience) the top level design of the code, and changing it may require rewriting almost everything. This is particularly true in a microservices world, where the problem may often be how you split a computation task up into services in the first place.