One modern PC server with PostgreSQL can handle about 1 mln transactions per second.
http://akorotkov.github.io/blog/2016/05/09/scalability-towar...
http://akorotkov.github.io/blog/2016/05/09/scalability-towar...
That's not average hardware. It's a couple hundred connections max running select statements as fast as possible on the best hardware they could afford to test against.
That doesn't translate into your CRUD app handling a million requests per second.