At a previous education startup I did a lot of interviewing of candidates. The question I feel gave me the most insight into candidates was very, very broad. After explaining (generally) how the company’s product worked, I’d ask them something like, “Let’s have a conversation about how you would design a system to distribute e-textbooks to students.”

I would reassure them there is not a right answer, that the exercise was just asking them to engage with the question. It was so effective as an indicator of future performance, and, according to those who eventually were hired, felt fair to them.

Of course this implies all my biases to people who can have a 1:1 convo about a very vaguely specified problem and so on. No idea if it’d be positive for everyone, but I wish someone would interview me like that.

Exactly, after years and years of interviewing and building teams I learned that the best way to interview about data structures is to do Q&A related to them.

Even if you are going to work in a project that requires building such structures, I demand that you don't do it from memory, but make sure to get help from resources to ensure that your structures are sound.