The interview question I stopped asking, and what replaced it

For most of my career as a hiring manager, my go-to senior engineering interview was a whiteboard system design question: design a URL shortener, design a rate limiter, that kind of thing. I stopped asking it about three years ago, and I think the interview got meaningfully better as a result.

The problem wasn't the question itself. It's that whiteboard system design measures a specific, narrow skill -- can you produce a coherent design under time pressure, live, in front of an audience -- that has almost nothing to do with what senior engineers actually do day to day. In fifteen years of engineering leadership, I have never once watched a senior engineer design a critical system alone, on a whiteboard, in 45 minutes, with someone watching and interrupting with clarifying questions. Real system design is iterative, happens over days, involves written docs, and gets challenged by other people with context you don't have.

What replaced it: I now ask candidates to critique a real design document, one I've written myself with deliberate, realistic flaws in it -- not obviously broken, but the kind of tradeoffs a smart, tired engineer might make without fully thinking through the consequences. I give them 20 minutes to read it alone, then we talk through what they'd push back on and why.

This measures something much closer to what actually matters: can this person spot a real problem in someone else's work, articulate why it's a problem in a way that would actually land with the original author, and suggest something better without being needlessly harsh about it. That's the actual job. Nobody designs systems from a blank whiteboard in isolation; everybody has to evaluate and improve on existing designs, usually written by someone who isn't in the room.

The other benefit I didn't anticipate: it's a much better signal for how someone will actually behave in code review. Candidates who are gentle-but-clear in the interview tend to be exactly that in real reviews. Candidates who either can't find real problems or who find them and communicate them poorly show that same pattern once hired. The whiteboard question never told me anything about that at all.