I agree in general, but I think bugs are a lot easier to track down with divide and conquer strategies. If you're able to reproduce the bug by sending request

I agree in general, but I think bugs are a lot easier to track down with divide and conquer strategies. If you're able to reproduce the bug by sending request X to service Y, gradually shrink the test case down until you've found the culprit. Optimization is often an architectural problem. Sure there are cases where you're copying a thing where you could recycle a buffer, but you run out of those fairly quickly, and a profiler will tell you what you need to know. A lot of the big performance wins are in changing the entire data logistics, possibly eliminating significant portions of the flow until the code does what it needs to in as few steps as possible.