I'll have to start and end this review with my personal opinion: I cannot get how a Hackerrank coding test can be relevant for a Senior Software Engineer job. Feels like lazy gatekeeping or a lack of general competence from whoever designed this process.

Start with immediate automatic hackerrank challenge, sent after submitting the application. Once you correctly solve it, got a call with HR. A lengthy call to talk about your experience, their type of work and align expectations. These two parts were very quick, almost instant. After that the the technical team decides if they want to move to next phase with you based on your CV and HR notes, which unfortunately I didn't pass. But the HR was very pleasant, and they were the only ones to give me very valuable feedback on why they passed which helped me to significantly improve my CV.