The HR were really nice. A very pleasant interview experience. Had two phone screens first with an engineer and then with the hiring manager. Both were very pleasant and nice to talk to. Questions had to do with Operating Systems and networking basics. Was invited for an on-site in Palo Alto. Checked in and waited for the first interviewer to receive me. I was taken to a conference room. Had 6 interviews in one day with 5 engineers and lunch with the hiring manager. 5 of the interviewers were really nice to talk to and the interview was a pleasant experience. 1 interviewer wasn't so nice to talk to. Avoided eye contact and seemed to have an attitude of superiority. Asked an ill-phrased design question. Other questions were mostly on the Linux kernel and OS internals. Very heavy on OS concepts. I'm a networking guy so couldn't get through. Overall a very good experience with both the HR and the engineering team. No doubt a great company to work for.