“To be frank, it wasn’t a completely straight path from point A to point B.”
Retool’s entire cloud product sits on one 4 TB Postgres server in Azure. They stayed on 9.6 until end of life forced the move. A dump and restore would have meant days of downtime, so they used logical replication to fit a one-hour window. The lesson is that everyone runs one giant database and upgrades only when the deadline hits.