Pretty common senior level product designer interview process from my experience:
1) Phone screening w/ their internal recruiter (who was super helpful through the entire process in subsequent phases in the process)
2) Rapid fire phone interview w/ the VP of design (I was applying from a remote location with the intent to relocate for the right job)
3) 3-4 hours of webcam interviews; one session w/ a co-located designer, one w/ product management, one with a few lead engineers and QA
4) A take home design assignment (suggested time 5-6 hours, but I definitely spent 12+)
5) An day-long onsite interview with the SLC team; team intros, white boarding activities, assignment presentation with critique / Q&A, and a really fun lunch where we all piled into a van and got tacos.
All-in-all it was a lot of time commitment, but on par with my experience interviewing senior level designers and being interviewed at various places.