If you're looking for people with the proverbial "smart and gets things done" properties, you need to give them something to do and see how smart their solution

If you're looking for people with the proverbial "smart and gets things done" properties, you need to give them something to do and see how smart their solution is. I give a task, like "write some code to store data in X; here's the interface I'd like to use" or "write some code to find X given data set Y". The problem should have "layers" and follow up questions. Some devs recognize the task and says "this looks like an application for $FOO" and apply some $FOO. Others do not know the name of the optimal technique, but are able to derive it on the spot from first principles. Junior devs should at least be able to come up with a brute force solution that solves the problem, even if they can't take it to the next level. If the problem requires some deep "ah-ha" moment then it's not a great test; the whole point is to separate applicants into strata.