If you come from the perspective that an interview question is a chance to learn how the candidate thinks then this is undoubtedly a bad question. Secondly it

If you come from the perspective that an interview question is a chance to learn how the candidate thinks then this is undoubtedly a bad question. Secondly it doesn't really give any signal positive or negative wrt to full stack developers. I mean if someone does't know how an index works it doesn't mean they can't use them effectively. And if they can answer it, it also doesn't mean they can use them effectively. Maybe turn the question on its head and ask....What possible info do you expect to get out of a candidate when asking this question?