Revolut Python Backend Engineer interview questions

There is 3 different steps in the interview process. I made it until stage 3 but have been rejected. 1) Phone Screen interview with the recruiter via Google Hangouts. - Personality, motivation, salary expectations. No technical questions. 2) Coding task to do in 3 days (SQL task - algorithmic skills testing - REST API - unit testing). - Received a very complete and constructive feedback on what I've done. 3) On site interview with Data tech lead and Data Engineer. - Technical questions and live coding task. People were really nice and friendly. But I was a bit frustrated because the on-site interview was really focused on Data Engineering, not much on Software/Backend Engineering.