[Agingcoder]

A quantitative view of a system : how it scales, what's possible / not possible ( because of hardware, software, algorithms, etc).

Basically, by knowing quantitative bounds of your system, you can make much better / quicker decisions.

[a_square_peg]

I agree 100% - I think this ability to identify the bottleneck for the system becomes more important as you move up the rank because you don't need to be the one doing it but you do have to know what needs to be done.