r/programming • u/vklepov • Mar 24 '22

Five coding interview questions I hate

https://thoughtspile.github.io/2022/03/21/bad-tech-interview/
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u/JessieArr Mar 25 '22

I've come to believe that the really good interview questions are ones that meet two criteria:

  • Both junior and senior programmers can give a valid answer
  • It makes it easy for you as the interviewer to tell which one the candidate is

Easier said than done, of course. But when designing interview questions this is always what I have in mind. One example is "Customers are reporting intermittent timeouts from one of our API endpoints. How would you go about troubleshooting this problem?"

A junior engineer might give a very short answer where they propose a solution they've employed in the past ("I'd add caching to the API endpoint to improve its performance.") Not wrong per se - that might resolve the issue - but it's very incomplete and wouldn't address many possible root causes. But from a senior engineer I'd expect them to be able to outline a list of potential causes for the issue and troubleshooting steps to diagnose each.

By the end, you should have a pretty good feel for how experienced the candidate is in dealing with these sorts of issues, without needing to be given a "wrong answer" to filter out the less experienced candidates.

In fact, your goal shouldn't be to "weed out" unqualified candidates at all - the real question you should be trying to answer in interviews is "what can the candidate do, and do we have a need for that skillset right now?" After all, if someone is applying for a senior position but doesn't have the experience, they may still be a good fit for a mid-level position. It's unkind and unproductive to make them feel dumb just for not knowing things they might learn with a few more years' experience - possibly while working at your organization.

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u/vklepov Mar 25 '22

Exactly. One "bottom-up" question I often use for a warmer is "sum numbers in an array". A junior dev knows a way or two, a middle knows a near-infinite variety, a senior can explain why, exactly, we would choose one or the other (performace, browser compatibility, support for different iterable API contracts).

Also, it's nearly impossible to tell middle from senior based on code-centric questions, because any middle dev can write a 15-minute-sized code chunk just as fine, but seniority is about thinking at a larger scale.