It depends on what you mean by performance. If you mean micro-optimisations like converting hash access to array access then these can matter somewhat if you are trying to handle large volumes of data or requests but the benefits tend to linear in the amount of data your process. That is by making 1 cycle of processing 10% cheaper, you knock at most 10% of the whole process.
On the other hand there are optimisations like using quicksort instead of bubblesort or using a heap for a priority queue rather than an array or a linked list. These are the sort of optimisations that change your program from take n^2 second to n*log(n) seconds. This can be the difference between "it finishes after an hour" and "I left it running all weekend and it's still not finished".
These days performance tends to only matter for scaling up. We tend to have plenty of memory and things tend to finish faster than we can notice so
