I think you're probably better off avoiding a trap or a trick here, and instead just ask about it. "Give me an example of a time you over-engineered something"

I think you're probably better off avoiding a trap or a trick here, and instead just ask about it. "Give me an example of a time you over-engineered something" and "Give me an example of a time you under-engineered something". Most people should have reasonable answers to both, and the one they have the most trouble with is probably the one you should be more concerned about.