I failed a system design interview for saying use postgres for the whole solution. App data to support about a millions users and a job/task table to support as

I failed a system design interview for saying use postgres for the whole solution. App data to support about a millions users and a job/task table to support asynchronous tasks. The throughput was a few tasks per user per day. I feel they were expecting a more complex solution with kafka queues. He! Interviews don't go well for saying "just use postgres"