Technical Interviews
Over the last year, we’ve done dozens of interviews that involve some kind of technical element. We’ve hired some great programmers, and we're looking for more
We’ve spent a some time thinking about how we run these technical interviews (as have others), so I wanted to touch on the kind of things we look for, and what the interview process at GoCardless looks like.
CV & Github
We ask everyone to provide a (brief) CV and links to their github account or other examples of code they’ve written. One page is usually sufficient - we want know about;
- Education
- Previous jobs & specific responsibilities
- Passion for development outside work. This is the area where people can really shine. Tell us about a hack-weekend project, open-source project or technical conference presentation that you’ve given.
Product & Business Case Studies
Even when interviewing for technical roles, we spend a fair amount of time talking about business & product issues. We think we can build a better company by working with people who are self-sufficient, take initiative and get stuff done.
This doesn’t mean you need a degree in business microeconomics, but you should have thought about questions like “what impact might feature x have on sales conversion, customer churn or revenue-per-user?”
Another favourite is “We have problem Y that is costing us £z per user. What are the technical solutions to this problem? And what are the business solutions? Which would you implement first, and why?”
Technical Interviews
This has been discussed at great length, but I wanted to throw in our two cents;
We use a couple of simple programming exercises - usually involving some kind of choice between recursion or looping, with a discussion of which might be more useful & why.
I personally think exercises like implementing Pascals triangle (where the candidate is given a definition of Pascal’s triangle, a choice of language and access to API documentation for that language) are really great negative filters that reveal whether a person can actually code.
We’re looking for something like
def pascal_loop(n)
triangle = [[1]]
(0..(n-2)).each do |i|
this_row = [1]
(1...triangle[i].size).each do |j|
this_row << triangle[i][j-1..j].inject(:+)
end
triangle << (this_row << 1)
end
return triangle[n-1]
end
We also talk through various theory questions, focussing on concepts behind web programming (transfer protocols, request-response cycles, persisting data, caching), database & systems design. We also touch on algorithms, but I’m not sure how useful this is, particularly for someone without a formal CS degree.
How do you run technical interviews? Comments welcome.
If you’re looking for a developer position in London, apply now!