I reached out to one employee on LinkedIn, networking with her and she referred to the position. I had four 30-min interviews, first with engineer, hiring manager, director, and then a manager from other department. All took one week. They all aksed me thoughtful questions about the details of my previous research. Feel like they want to know that you really understand and engaged in what you do and not just participate. I felt good about the first three interviews until the last one when I couldn't solve the quantitative problem correctly. The last one aaked me about an experience thats unrelated to the job and I couldnt answer clearly. I didn't hear back since then. Overall, it was a good experience and I actually felt more inspirational after talking with them. They are all genuine people and I have learnt a lot during the process.