In a few of my how does it work? posts I’ve mentioned that asking about a particular data structure or algorithm is a boring interview question that doesn’t tell you much of anything about whether your candidate can code.

First of all, the reason I think asking someone to implement a data structure or an algorithm is boring is because all you learn by doing that is whether or not your candidate looked it up beforehand. Not even that, necessarily. Interviews are pretty stressful and plenty of people’s minds go blank when they’re stressed. I once choked on a question about the servlet lifecycle and it’s not like I don’t know how servlets work. If a question might tell you one thing and might tell you nothing, I don’t think it’s a good use of the limited amount of time you have in an interview.

Unrelated image from to make this post look nicer in social media shares.
Unrelated image from to make this post look nicer in social media shares.

I hate ridiculous brainteasers for the same reason – they’re just so binary.  Either your candidate gets the right answer or they don’t, which may or may not tell you anything because a stressful situation where you’re really scared of looking stupid is basically the worst possible environment to solve puzzles in.

Given all that, it seems fair to ask “Well what on earth should I ask in an interview?”

My take on it is that we’re overcomplicating the question. Which is kind of an occupational hazard, so don’t feel too bad about it :) Basically, if you want to know if someone can program, ask them about programming! Just straight up ask them how they would solve a problem.

One of my many pet peeves are wildly improbable scenarios questions like how many piano tuners are there in New York? Google, that’s how many. If you want to know how someone approaches a problem, just give them a programming problem. I really think it’s just weird to dance around the subject you really want to know about. You are allowed to straight up ask people about programming! It’s not as if programming problems are thin on the ground either (hey, what do you do all day again?), although it does take some work to find a problem that doesn’t require twenty minutes of backstory to explain why the problem is a problem. And if you’re asking improbable scenario questions because you want to see how a person thinks about a problem without them jumping directly into code, I think you’re depriving yourself of useful information. If somebody jumps directly into coding without thinking the problem through, I want to know that!

The kind of questions I think are interesting are realistic-ish (obviously you need something relatively simple if you want to ask more than two questions before you run out of time) scenarios like “given a system like x, how would you add feature y?” and “how does your solution change when you discover that the system is actually more like q than like x?” or “what would you do if production went down or was painfully slow?” or “given this description of a weird bug, what would you do to track it down and solve it?”

While every interviewing method has flaws, I like the idea of giving someone a take home project that either takes under two hours or that you pay them for, then talking about the choices they made in the interview. If you want to know if someone can code, just ask them to write some code! But for the love of god don’t ask them to do it on a whiteboard, that’s ridiculous. Coding on a whiteboard in no way resembles what a programmer does all day, even if your candidate is good at it it’s simply irrelevant to the job you’re trying to fill.

The downsides to take home projects are that they’re very biased in favour of people who have the free time outside of work to do them and that like everything else, it’s very very easy to do them badly. I’m willing to spend an hour or two on a take home project, but any more than that and I expect to get paid for my time.  That’s coming from someone who has no children, no pets, no elderly or sick relatives to look after, and practically no chores to do, too. For people who do have responsibilities, asking them to spend n hours of their scant free time on you is a big deal and you need to keep that in mind when you design your take home project.

Which is the other potential problem with take home projects: they need to actually take the amount of time you say they will. Yes, that means you need to have someone at the level you’re trying to hire for solve it first. I would say solve it yourself, but if you’ve been programming for ten years and you’re trying to fill a junior position, you need an actual junior to make sure what you’re asking for is reasonable.

That said, even the worst take home project is much more realistic than the ridiculous idea of asking people to take a short contract with you to see how they actually work with everyone in the office. There is basically zero chance anyone with any responsibilities is going to think “Sure, I’ll definitely quit my stable full-time permanent job to take a two week contract with some yahoo who might hire me if they decide they like me. What could go wrong?” That said, if you’re looking for people you can exploit, by all means keep hiring that way.

On a more cheerful note, a really good idea that came from a discussion on slack is having the candidate read some code and explain what it does. Most professional programming involves way more reading code and making sure you understand it, so much so that it seems like a really good idea to test people on that directly.

In general, ask stuff that directly relates to the job you’re asking someone to do. If you really do want them doing algorithm design then fine, ask them about algorithms. If you’re doing web apps, ask them about the frameworks you use or about general web concepts like concurrency, multi-threading, sessions, basic security, etc. If you do consulting, lean a little harder on scenarios where the candidate needs to ask questions to figure out what the client really needs, which is usually not what they asked for.

What do you think, readers? Do you have any favourite interview questions?