Comment by gutnor

Even if you have used them like a few months ago. Very few people work on variation of the same problem over and over again, except in research.

Generally, you have a problem, you research, you experiment and then you wrap all that in a nice easy to use utility class or api and forget the details because there is something else you need to work on and that problem was just one piece of the puzzle anyway.

The worst hypocrisy in all that, is if you ask a specific question to a veteran developer on a average size codebase, he will very often need to look in the code and you will not think any less of him. But if it is an interview and he does not remember some trivia in a piece of code he didn't write - my god, he is a loser.