This process was a few months ago, so apologies if I forget anything. The interview process starts with a short HR screening and then an online assessment through Hackerrank, I don't remember exactly what my question was but I didn't think it was difficult. After that they asked for my college transcripts. I was then directly moved on to the onsite interviews at their headquarters.
The onsite consisted of 4 interviews, plus lunch with two junior engineers. The first interview was a design question, the second was a straight Leetcode one (two questions, neither were very difficult). After lunch (which was a casual sort of environment with the two engineers, basically just chatting about their work and all that) was my third interviewer, who was absolutely awful and really the sole reason I'm leaving a review.
She came in late, and seemed very flustered and new to interviewing. She proceeded to whip out a literal notebook containing her interview questions, in plain sight of me on the table. First question: "do you know FizzBuzz?" I answered yes, because literally everyone knows FizzBuzz and I didn't think she was asking me to do it. Then she acted surprised and said she was going to ask me to solve it. Yikes...then she seemed very flustered because she didn't expect me to know FizzBuzz, and moved onto a very contrived and unclear piece of pseudocode she came up with on the spot. She kept changing what she was asking when I asked for clarification, because it was clear this wasn't a question she had beforehand (in a notebook of interview questions, she really basically only had FizzBuzz?). Eventually it became clear she was asking about inheritance, but her example code was really poorly written. After that, she was fresh out of technical questions (and admitted it) so she just started asking me about my project experience to "fill time".
Finally, my fourth interview was pretty short. He just asked another design question, and that was it. The process was fairly smooth with HR, and my recruiter contact was a nice guy and pretty responsive. All my interviewers were nice and good to talk to, even though the third interviewer was a bit of a mess. The office seemed pretty hip and had some standard tech company amenities, and I appreciated being taken out to lunch. Now, that being said, I still have to wonder if I would have received an offer if I had just pretended I had never heard of FizzBuzz before...