First by phone, then in person in Cambridge. The in-person was with other young Quants, and with the lead, and with a higher exec. Friendly and asked both technical questions and tried to gauge my goals and see if I could be valuable.

Really pleasant interview experience. It is lengthy, but I thought they were pretty transparent throughout the whole process (regular updates, giving feedback, taking feedback etc). Starts out with a very easygoing and laidback phone screener, and then progresses to meetings with various members of the team. You'll be asked a few behavioral questions and then a few brain teasers in each team meeting. I've seen a lot of reviews here complaining about the brain teasers, but in all of my interviews they weren't too hard, and the interviewers helped nudge you in the right direction as long as you were enthusiastic about trying to solve it. Don't expect a drill seargant interview, but also don't expect interviewers to just go through the motions. They will ask you pointed follow-up questions and they will ask you to expand on things. As long as you're not BSing anything on your resume you'll be fine.