Chill process and quick 30mins. You need to be clear and succint. They don't ask you to share your achievements (already in resume) and they want to know challenges and how you overcame those. The rest is culture fit questions.

First round was a 30 minute call with Recruiter. She asked 3 questions and said everyone was asked same 3 questions. Second round call was 30 minutes with Hiring Manager, she asked a few job-centric questions and left time for questions. Third round interview was on site for total of 5, 30 minute interviews. I spoke with hiring manager again, with 2 people in role I was interviewing for and then 2 adjacent team members. Facebook HR sent "sample" questions before final round, most of the questions I faced in interview came from this list. Didn't get offer but Recruiter took time to call after and share my strengths and weaknesses and offered to help me find other roles in company.