3 phone interviews, first with technical recruiter, second with hiring manager, third with principle engineer. 2nd and third phone interviews required a portfolio to go over showing designed hardware. Then they flew me out and interviewed me for 8 hours straight in person. In person requires a presentation to the team. In person also had ~10 one-on-one interviews going over whiteboard design and analysis questions. Grueling process, but very fun. Didn't get an offer - cited that I knew the governing mechanics of the whiteboard design questions but I didn't identify the critical failure points fast enough as the primary reason.