Some of this can be reduced to a trivial form, which is to say practiced in reality on a reasonable scale, by getting your hands on a microcontroller. Not RTOS or Linux or any of that, but just a microcontroller without an OS, and learning it and learning its internal fetching architecture and getting comfortable with timings, and seeing how the latency numbers go up when you introduce external memory such as SD Cards and the like. Knowing to read the assembly printout and see how the instruction cycles add up in the pipeline is also good, because at least you know what is happening. It will then make it much easier to apply the same careful mentality to this which is ultimately what this whole optimization game is about - optimizing where time is spent with what data. Otherwise, someone telling you so-and-so takes nanoseconds or microseconds will be alien to you because you wouldn’t normally be exposed to an environment where you regularly count in clock cycles. So consider this a learning opportunity.