Very long. Went through at least 3 rounds, each one lasting at least 4 hours, plus a written assignment, plus and online behavior assessment. I met with other engineers, the hiring manager, the president, the head of HR. Sometimes it was one on one, sometimes in a group. I was okay with it, it was just really long and thorogh. After each round I was thinking I was ready to get an offer, and I'd find out that I had to come back for another round of interviews.