Absolutely. At my last C++ job, I did a lot of interviews and a lot of people claimed to know the STL. I left the low-level compiler questions to my colleagues

Absolutely. At my last C++ job, I did a lot of interviews and a lot of people claimed to know the STL. I left the low-level compiler questions to my colleagues for the most part, but I would ask a few key questions. My favourite STL-related question to ask is simple and can be done on a whiteboard in minutes: if you didn't have std::set<class T>, but you had everything else in the STL, how might you implement a set<class T> class? There's an ideal answer[1], and then there's people who start thinking about low-level implementations. The ones who I don't want are the ones who don't have any answer at all. I'll continue to be interested in anyone who starts talking about the way to solve the problem. What matters to me is not any code that you write (although that's interesting) but your thought process. After the candidate has worked through this, if they haven't gotten the ideal answer I always give it to them: this isn't some national secret, and seeing them process the ideal answer and realize that yes, it really would work is a pleasure. Sadly, there are cases where it doesn't work. I had one candidate who did very well on the phone screen, but didn't know the STL. I looked up what he claimed to know (Qt) and reframed the question in terms of Qt's classes—and he still couldn't come up with any answer whatsoever. -a [1] The ideal answer is precisely such because you're writing much less code and using stuff that people smarter than you have written. It's to use a std::map<class T, bool>.