Throughout the process the recruiters were extremeley good at keeping me in the loop and up to date along with setting my expectations as to what was coming up, probably the best experience I've had interviewing. My process looked as follows:
1. Long codility test. Questions were 1 leetcode style easy level, 2 leetcode style mediums. Was encouraged by recruiter to program in C++.
2. Phone interview. Very technical questions on low level programming and concurrency and an easy C++ question. We got down to assembly and beyond in the low level question.
3. On-site. Three individual interviews with 5-10mins at start with questions about my CV then whiteboard problems. More leetcode style problems with some space for low level performance considerations. Some C++ questions and general SWE questions such as design patterns, testing etc.