The recruiter kept changing the interview process as we went; at first they told me it would be 3 rounds (and I sailed through 2) and then it turned out to be 7 rounds (!) and none of them were with the hiring manager. The last 4 interviews were all at once and they were asking me questions for things that would not be a part of my role, since the interviewers were from other teams. I don't know if this is typical or if it's because my team was in flux, but I will not be applying at Twitter again after this experience.