I wouldn't ask someone to whiteboard it but I think "what is a hash table?" is a brilliant interview question. The depth someone can go into tells you a lot and

I wouldn't ask someone to whiteboard it but I think "what is a hash table?" is a brilliant interview question. The depth someone can go into tells you a lot and can bring up lots of other topics to discuss. It tells you a lot if a senior developer doesn't know what a hash table is or only knows "it's a class from Java" too.