They have a big open funnel and put everyone through it, clearly using the series of 7 x 1hr interviews to grind down the volume of applicants to a manageable number. Setting up the interviews was simple email responses and the coding interviews themselves were not nightmarish leetcode/hackerrank puzzles, but a non-trivial base puzzle, then two possible "level-up" extensions. There was one person presenting the puzzle and evaluating your progress, I sense done by ticking items off on a checklist. "applicant did this", "said that", "did not do the other". Time will be your critical restraint. Feedback at each successful phase was next day, but took 10 days and considerable prodding when I failed.