Series of 1 on 1 interviews that were mostly technical in nature. The interview process was started with a presentation on a subject of your choice (graduate thesis, project at school, etc.). They grill you after this presentation. The one on one interviews were mostly technical questions to see what your thinking process was. Mainstream also takes you out to lunch in the middle of the interview process.

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.