As a candidate, I’ve had some interesting (and some stupid) questions come my way. Like: If you were an animal, what animal would you be? How would you work out how many glass windows there are in the city? What is the volume of water that flows through a cylinder with a radius of x, and the water is y high (asked, oddly, of someone interviewing to manage software engineers, not pipes). What these have in common isn’t just that they are stupid questions, it’s that they are one-directional. The candidate performs, the interviewer judges, and that judgment never makes it back to the candidate. To be fair, I’ve probably asked my share of bad questions as an interviewer. But over time (and I’ve probably interviewed more than a thousand people), I’ve settled on this as my favourite and most valuable question to ask at the end of an interview: "I’d like to give you some feedback. First, so you can get some feedback on the interview, but also so you have the chance to correct anything that I have misinterpreted. Is that ok with you?"

Ok. It’s not really a question. The ‘is that ok’ isn’t really seeking permission; it’s giving the candidate a few seconds to prepare for what’s coming. As in, "I’m about to shift from interview mode to feedback mode, here’s a moment to reset." The valuable bit isn’t asking that question; it’s what happens next that’s valuable. From there, I go into depth with feedback (also inviting the other interviewers to do the same).

So, regardless of what else you ask in the interview, this question makes the interview two-way instead of one-way. The feedback I give is then highly opinionated, direct and transparent about what I’m thinking. I will talk about both what was positive and my concerns. On the positive side, I have said things like: "Your architecture walkthrough was clear. You explained the context well, clearly stepped into each level of the architecture and explained the tradeoffs well, showing us that you are senior and have a solid grasp of architecture concepts." On the constructive side, I have said things like: "When you explained to me how to get a team to deliver effectively, you described how you have worked in the past, and the mechanics involved there, but when I pressed for more on how you’d get a team delivering effectively, I didn’t get much beyond what you’d already described."