I was an internal referral and went through a somewhat different route than usual.
I was interviewed by the other senior engineers, PM and a recruitment director on video and overall had a pleasant experience discussing the minutia of scaling a large distributed application, of the software life-cycle, of caching and invalidation problems.
I was impressed with the overall knowledge of the people interviewing me and that contributed to my decision to accept the offer later.
Since I was interviewed remotely, I asked for an in-office visit to "feel the culture" and talk with some more employees. From watching the lunch/break room and seeing people smiling and happy (and playing board games and card games during breaks) I got a strong sense of team spirit.
Note: I was warned that "coming without high energy levels" might be a problem, as this is a startup environment and not "corporate america". Since I actually wanted a place like that it I liked that statement.