I'm certainly not against micro-optimizations. But they are very context sensitive and cannot be done without proper profiling of the whole program using repres

I'm certainly not against micro-optimizations. But they are very context sensitive and cannot be done without proper profiling of the whole program using representative workloads. I find people are often writing spaghetti code because they heard it's "faster". That said I would draw a distinction between implementation and design. The surface API needs to be well thought out before hand. But this should be done before writing any real code (exploratory code aside).