Agreed, breaking your concentration to type is bad and rather easily mitigated. However, the time required to break the flow of whatever you happen to be doing

Agreed, breaking your concentration to type is bad and rather easily mitigated. However, the time required to break the flow of whatever you happen to be doing is very small. Imagine you could type instantly. As soon as you thought of what you wanted to type, it was there. Moving a block of code or an expression into a REPL and evaluating it would be immediate. The first bit of boilerplate for a new project wouldn't get in the way of thinking about what you're actually working on. None of your time would be spent on the mechanics of transcribing. Is it a minor optimization? Definitely, especially given the real limits on human tying speed, but anything that keeps you in the zone is going to add up over time. In my opinion, it's not that typing is a bottleneck, it's that breaking concentration for anything is one of several bottlenecks. Edited to add: As I think about it, I may have failed to draw a clear distinction between "breaking concentration to type" and "breaking the flow", and in fact went back and forth on the wording I used to refer to each. To summarize, I feel that breaking the flow can happen anytime you have to wait on something, be it physically typing a command or bit of code, waiting on compilation or evaluation, or glancing up at and thinking about a notification. Build times are largely out of your hands and people will always interrupt you (in person if you mute notifications), but physical typing delays are solely in your own hands and eliminating them can help keep you in the productive flow.