Are you asking this from a DBMS internals or an application perspective? Are you posing it as a "one true answer" type question about a specific DBMS? I'd expe

Are you asking this from a DBMS internals or an application perspective? Are you posing it as a "one true answer" type question about a specific DBMS? I'd expect any software engineer or CS grad to be able to make a reasonable guess at how a secondary index might work internally. I'd expect any experienced software engineer who has worked with databases to be able to explain the application side aspects of "how an index works". e.g.: What access patterns a given index would help with and which it would not help with, what the downsides of having an index are, etc. Though even an inexperienced engineer should be able to derive answers to these questions once they've made a reasonable guess at the internals. I think a lot of people are responding to this negatively due to viewing it as a trivia question whereas it can actually be a "reason through what has to happen to make something work" class of question.