Interview process is
Hiring Manager -> Technical -> C Level
Declined at the technical stage.
As another user pointed out, there is a take home package you are given with three questions a few days before your interview.
There is a lot of ambiguity in the questions and the interviews expect to see a lot of different answers. That being said, the decision to put one through to the final round seemed to be decided on before the interview even took place which was disappointing. Also similar to what the other user on here mentioned, it seems they are fishing for ideas on System Design and not interested in making a hire.