Uber Sr. Software Engineer interview questions

A recruiting firm applied on my behalf. Interview was quickly scheduled. Their recruiter was responsive and process was smooth. The first round (coding) didn't go well for me, but interviewer probably considered my experience and sent me to second round (design). The interviewer was great and gave ample hints. The design round was horrible. The main interviewer was shadowing someone who was obviously not qualified to take design rounds for senior folks. He kept interrupting me throughout the interview. The design problem was very rudimentary for a 7-8y exp candidate, and the interviewer even failed to ask good questions on reliability etc. Uber rejected me after this round, and I wasn't surprised. Still unable to understand the logic behind using unqualified interviewers for senior folks, felt disrespectful to me.