Three interview sessions.
First a phone screening with recruiter, very simple.
Second is a technical interview with an engineer, wherein a couple fundamental questions are asked.
Last is an in-person interview, where they fly you out. The day starts with an initial one-on-one interview. After this, you give a 45(ish) -minute presentation plus questions. Next, you have two more one-on-one interviews, then go out to lunch with some younger engineers at the company. After lunch you go on a tour of the company grounds, and then you have two or three more one-on-ones. Each of the one-on-ones last 30-45 minutes each. Only a couple of the one-on-ones are very technical where they layout a problem and ask how you'd solve it. Overall, it was a great experience with a great company.