I do a bit of performance work and find most often that things are mixed: there’s enough CPU between syscalls that the hardware isn’t being full maximized, but there’s enough I/O the CPUs aren’t pegged either. It is rare that the profiler finds an obvious hotspot that yields an easy win; usually it shows that with heavy refactoring you can make 10% of your load several times faster, and then you’ll need to do the same for the next 10% and so on. That is the more typical real world for me, and in that world Python is really awful when compared to rewrite-it-in-Rust.