The interview process was full of difficult and exciting challenges, I really liked it. First, I got a very easy algorithms challenge on HackerRank, then a tougher challenge involving parallelism and data structures. After that, I had two technical interviews, where I both described my experience, answered questions about many fields (algorithms, design patterns, security, web application programming, architecture). After that, I had an on-site challenge (which I took remotely :-P), and I had to transform an application written in a programming language I had never seen before. I really liked that one, it was cool and exciting. After that, another technical interview and a culture interview with the CEO.
My process was a little atypical, since because of a mistake I had more technical interviews than I should have had. Also, the current process is simpler, some of the challenges have been removed.