First round, he directly jumped asking scenario-based questions on MQ and transactions in DB.

There were a few questions on indexes, with no Java questions.

I answered the index-related questions correctly. For the scenario-based questions, it seems he had a fixed answer in mind, and he wasn't satisfied with my responses.

What is an index?

What is a clustered index?

If you have pushed 900 transactions to MQ and the queue stopped responding, but you still have 100 transactions to push, how will you handle this?

If 100 transactions are there in the DB, you have to pick 20 transactions out of those. Process 10 and skip 10. Whenever the scheduler job runs next time, you should not pick the processed 20 transactions for the next run.