HackerRank test like everyone else described, then phone call with recruiter, followed by phone screen, take home coding assignment, then onsite. Unfortunately, they only give you a ride to and from the airport to the office, unlike some other companies I've interviewed with where you can expense your travel to the airport you fly out of, as well as meals.
While the people I talked to were all very nice, I have to say I was treated a bit rudely; I went through the trouble of doing a take-home coding assignment and flying out to their office, but they simply ignored my follow-up emails after my on-site for quite a while. It seems a lot of other people have this experience, which is too bad because I feel like they do have a pretty friendly culture there.
My interview was a software developer interview, there was zero "quant" stuff (e.g. probability, optimization, finance). The first interviewer somehow didn't know what a heap was, which was very weird. He asked some systems design kind of question but didn't communicate clearly and I had lots of trouble figuring out what exactly he was asking. The rest of the technical interviews were whiteboard coding. I thought I did okay as I pretty much got all of them, but no offer so perhaps not.
