The scale of operation is the crux here. For a modest number of cores, RDS is a congenial choice. However, when you're going to hundreds or, as in our scenario, tens of thousands of cores with PostgreSQL, clinging to RDS is sheer lunacy.

I was the designated gardener to tackle this: architecting and managing a PostgreSQL deployment with 25K cores and 3M TPS. We've been shelling out a cool $1M annually, covering the whole thing - hardware, software, and DBAs. Meanwhile, the toll for RDS is an astronomical tenfold of our current expenditure, yet it comes with a lesser degree of availability and a starkly crippled observability and other stuff.