I was originally not chosen for an interview but their first round of interviews didn't yield any candidates. First I had a quick phone screening with the recruiter with some basic interview questions, then they sent a coding and math/probability assessment. Then I had an interview with one of the higher ups with the math team where we talked more about my experience and went over some of the mistakes I made on the math portion of the assessment. Then I was chosen for a site visit where I met with some other mathematicians and did some more quick assessments, mostly to check my logic and basic probability and coding skills is seems.