It took some time to hear back after my initial online application (roughly 20 days), but from that point on everything was very quick. The interview process lasted roughly 12 days from the first email from the recruiter until the final 4th round. This included a 7 day buffer period to submit/take the first (timed) coding challenge which I utilized 5 days of. The last 3 rounds were fit into the remaining 7 days.
Round 1: Hackerrank coding challenge: Difficulty, medium-hard. A very quick, 60 minute timed challenge testing basic coding abilities as well as some advanced aspects. There were 2 easy coding portions, one easy multiple choice, one medium coding, and one hard multiple choice.
Round 2: Phone screen 1: Education/experience background/culture fit with the recruiter: I had an absolutely fantastic recruiter, she was super enthusiastic and you could immediately tell that she loves the company. She was extremely receptive of me as a candidate and was overall the most positive phone screen I have had to date. This process seemed more culture fit oriented, and she asked me about previous experience, and more about me as a person and how I got to the point I am at now, where I wanted to be in the future etc...
Round 3: Phone screen 2 (Skype): Technical screen regarding previous experience. It went over some very basic concepts regarding JavaScript and SQL. Some questions about previous experience listed on the resume as well as some trivia regarding the languages that I had listed on my resume. Everything was well organized, and the original scheduled start and end time was kept. This portion lasted roughly 25 minutes, but 30 were allocated.
Round 4: On site: A one hour on site interview. In person coding challenge involving SQL and JavaScript (separately). It was almost back to back coding, there weren't any breaks for anything. They did give me a very brief tour of the office. This step was initially supposed to be longer than an hour, however they accommodated my final exam schedule and cut it short at the request of my recruiter. I believe this portion is typically supposed to last 3 or more hours.