TL;DR; They are looking for the cream of the crop. Very high quality of employees and high standards. The Interview is hard, need to study as if you are back in University for this one.
Process was straight forward. I had received an email for an interview the week before. I had attended the first interview where I was asked about my experiences as a backend developer. Also how I'd architect a new micro-service from the ground up. Although its a software engineering position they require heavy understanding of the Computer Science field including terms and their application. I felt as if I was going in to do my thesis. I than proceeded discussing my previous experiences, which than I was told that I'd pass the first round and would go on to do a Hacker Rank assessment. I ended up not getting a passing score. They required a 70% to pass. I did all the questions except one. It was fairly straight forward. They asked CS fundamentals security questions, and then there came 2 Hacker Rank coding questions which was pretty difficult (You need to answer both). You are required to answer all 17 within the hour and 15 minutes given. The result of the assessment will come back in 24 hours. After that there are 3 more interviews, again grilling you on CS Fundamentals, component design and system design, a Leetcode round where you perform a task and answer questions on your solution while determining the complexity (Big O-Notation), Algorithms and their applications and a few behavioural questions.