The interview process at Aha! moved very quickly. I was referred by a former colleague of mine who had interviewed with Aha!, and the CTO reached out to me directly. I had a couple of conversations with him, and also spoke to another engineer on the team. Following the technical interviews, I had an interview with the CEO, which was more of an assessment for cultural fit.
The technical interviews were pretty in-depth, and probably on the harder end of the kinds of interviews I have experienced, but I never felt like I was dodging "gotcha" questions. It seemed like even questions that could have been construed as quiz-like always boiled down to seeing if I made technical decisions based on CS fundamentals and good research vs hype or gut feelings.
Through the whole process, I got the impression that everyone talking to me not only wanted to make sure I would be good for the company, but also that the company would be good for me - they were very clear about their values, what would be expected, and what success would look like in the role.