Duo takes hiring seriously, and the interview process was extremely solid. An in-house recruiter immediately made me feel at ease, and everyone that I talked to during the process was very friendly and enjoyable to talk to. I had originally applied for a position much earlier in the year, but was told that I would likely be a better fit for a different team within the company, and that they would keep my info on file -- I sort of thought this was a kind of way of turning me down, but about 6 months later they called me up and said a position had opened up, and they wanted me to come in to interview. The interview took about a full day, and I spoke to two managers, a director and a VP of engineering. There was a technical interview (standard comp. sci questions, including big O notation and unit tests), a behavioral interview, and two more conversational interviews in which they got a feel for my technical background and personality, and gave me lots of opportunities to ask questions and assess more about the company. Duo seems to be full of people who are actively working to make sure that the rapid growth the company is experiencing happens in a meaningful way -- they take a lot of pride in ensuring that the culture moves in a positive direction, and one value that was frequently touched on was "Be Kinder Than Necessary," and it showed in the sort of interactions I experienced in their office.