Should I use std::vector::at() in my code

Question

I noticed today that std::vector::at() is significantly slower than accessing values with square brackets []. According to the doc .at() i

Answer 1

at does range check, but operator[] does not. For example, if you pass -1 to at(), an std::out_of_range will be thrown. But if you do the same thing to operator[] it will crash or strange things will happen.

If you are absolutely sure that the index is OK or you want to do the check yourself, use operator[].