I was interviewed by two senior staff after sending my resume which appeared to be a good enough match. While the job description on different sites might vary and there is a long list of skills required/desired, by the interview it would seem they consider c++ the most important skill. You need to know/revise this well for the interview. While I didn't sign a confidentiality agreement, it is probably safe to say you should focus on practice the C++ skills and a bit of those first year maths so you are spending most time trying to deduce it yourself. The deep learning skills didn't seem to be part of the technical interview, which I assumed to be the most important and prepared accordingly. This is not Google like brainpuzzles and reasoning on algorithmic complexity. In retrospective, most questions were quite easy.