Writing correct code is about chosing correct data structures for the problem at hand as much as "coding". And chosing the correct data structure comes down to

Writing correct code is about chosing correct data structures for the problem at hand as much as "coding". And chosing the correct data structure comes down to understanding the performances (using Big-O / best-worst-average or Analytic Combinatorics) of the operations you're going to perform and the algorithms you're going to use on these data structures. It really sucks to have to refactor a codebase because some coder thoughts that lists would have been great there when actually a bi-dir map was what was needed (and vice-versa).