Most performance problems come from incidental complexity and programming techniques which don't take into account what the actual hardware is doing. Your focus

Most performance problems come from incidental complexity and programming techniques which don't take into account what the actual hardware is doing. Your focus should not be on tactical optimizations like caching but rather on expanding your understanding of the system as a whole in order to devise simpler and more efficient solutions to problems. Look into "data-oriented design" for more info on this. In the modern business environment, time is most often not allocated for optimization after functionality is complete. And even when it is, if performance is completely ignored throughout the development process, your options for improving it at the end are severely limited.