I found out about Mesosphere via Hacker News and applied through the careers portal of their website. Three weeks later I got an email from a recruiter. There was an initial phone chat with recruiting, a 4-hour take-home coding challenge, a follow-up call with an engineer about it, and then an on-site. The entire process took about 5 weeks, which was partially due to my own crazy scheduling issues. The coding challenge was practical, and the on-site was very typical of Silicon Valley: 4 x 45-60min whiteboard sessions with various members of the engineering team, lunch with potential future team members, and a chat with a founder.