I was referred by a friend and started off with a quick phone call from the CEO. We covered the business and what the company and I were each looking for. Next was an in-person chat with both founders, which seemed primarily to be after culture fit and whether we'd want to work together (hint: the founders are both great people who do an impressive job being accessible to everyone). I also met one of the senior engineers to make sure I was basically competent. The bulk of the interview was lunch and an hour with each of 4 engineers covering technical problems, plus an hour with the VP Eng about culture, engineering process, leadership and mentoring.
The whole process was two weeks from introduction to offer (and acceptance!). We both would have been happy to move faster, but for scheduling constraints.