I recently interviewed for a machine learning position at Google. There was essentially no focus on machine learning. I had 6 interview sessions total (5 onsite and 1 live coding phone screen) and 5 of those interviews had nothing to do with machine learning. In fact, those 5 interviewers had no machine learning background and knew nothing about machine learning. The one interview that was focused on machine learning was fairly straightforward and simple. It was kind of funny how large a contrast there was between the Google recruiter'a pitch ("we want to become an AI first company") and my actual experience interviewing. The interview process I went through has no way of distinguishing between someone with in depth machine learning knowledge and someone with basic machine learning knowledge. It was essentially a software engineer interview. I did not get the position, but I would recommend you look elsewhere if your focus is truly machine learning