The most talent dense place I've worked had a dead simple process - two one hour chats, one with your potential manager/team and one with the CTO or CEO. If things didn't work out, well you got sent away, probably happened twice per month. There was a particular meeting the CTO/CEO used and if you saw someone meeting with them there on a Friday afternoon, you would not see that person on Monday.

The place was not big - never got much beyond 100 engineers, but produced dozens of founders, VPs, GMs etc at well known companies, as well as engineers with very notable OS projects and lots of high-placed engineering in FAANG companies.