> if you understand how the CPU, memory, network, and disk are processing

I don't think it's possible in the general case, it's way too complex for that. Sure for trivial examples it's trivial to claim one program is faster than the other, but can you really claim that your special allocator used in one place plus the extra argument used in calling that function is worth it without writing both options and measuring it? Like even measuring it is non-trivial, will it be inlined at the use site, how is it called, etc.