Met them at a career fair and was contacted subsequently. After about a week, I had a phone interview that comprised of some basic algorithms questions and discussions on my prior projects. The interview was a little less than an hour long. I did really well and was then invited onsite. One of the scheduled interviewers did not make it and was replaced by some one else. There were 4 rounds. i) with manager: a really interesting problem but the goal was to only approximate the solution and which involved subtle nuances of low level arithmetic ii) algorithmic interview iii) question on OS synchronization iv) General interview in addition to discussion of my resume