It was 4 rounds of interviews.
I had a pleasant conversation with HR during my first round, which was more of a test of culture. 30 min
My second round was with the SVP and a manager. This was also cultural and some technical modeling questions. 1.5 hours
Third round was with the COO and SVP. This was about presentations and technical modeling. 2 hrs.
Fourth Round was with the COO, VP and the SVP. This interview was heavily based on cultural and technical. 2.5 hrs
I thought the interview process was a long one, but it was worthwhile. It wasn't overall difficult as more of a fit for personality. I believe the HR guide assume everyone should already be technically strong background from whom they choose.
It is best to be relaxed during these interview processes, but excited about what you are applying for.