And then, that senior dev will pick a newer, better CPU, on-device bus, network topology, or your setup simply has a different scale, and hard-learned heuristic “don’t use more than x foo’s for y” or “the network is the bottleneck; use huge machines” become obsolete, and your dev will get some new battle scars.

I guess that will happen in HFT all the time, as you don’t want that blazing-fast setup, you want something even faster.