> 2 bare-metals with Linux, Postgres, HAProxy and PHP (or Python/Django) work perfectly fine for 99% of apps that businesses need.

I agree. Simple and effective.

I would add a third small machine to give HAProxy a third vote. The problem with only two machines is that, if communications between them fail, you don't want both believing the other died and doing the wrong thing. You could use that third machine for Postgres backups, which would be smart because Postgress replication is not the same as backup.