Apple Data Engineer interview questions

There were two phone interview and an onsite interview with 5 interviews. Mostly SQL. The focus is on aggregate functions, window functions etc. There were database design questions also. There programming and data mining questions also. Overall it was a good experience. All the interviewers were nice. But at the end, the recruiter never told me the results of the interview. Even after mailing her multiple times. Did not expect this unprofessional approach from Apple.

Contacted by a team manager. HR reviewed application and asked to schedule an interview. Made multiple requests to make confirmation following which,\ a tech phone screen was finally scheduled for 30 mins, but it lasted for merely 5 mins (a complete bummer). A team member later contacted for further screening. Didn't hear back for interview confirmation, upon multiple requests, understood that OPT candidates have more 'screenings'. Didn't hear back at all.