I applied for the position through a referral. The first round was an online assessment that was based on HackerRank. I was able to pass all the test cases in all questions. But still got a reject without any reason.

Deep dive into past projects, anything that is relevant in software development would be asked, not only backend development. Then the interviewer posed questions about basic concepts and terminologies like locks, process management, memory management, database sharing etc. Ended with a medium Leetcode problem.