One database, held properly: vacuum and transaction-ID vigilance, index portfolios with real carrying costs, connection pooling, and schema changes that do not lock a busy table at the wrong moment.
Postgres runs every case study on this site. This shelf is why it runs them calmly — and why the one metric worth alerting on is transaction-ID age, because bloat warns you and wraparound simply stops your writes.
Boring database, sound sleep. That trade is one every operations team eventually accepts, ideally before 3 AM teaches it.
Nothing here is exotic tuning. It is the small set of behaviours that separate a database you operate from one that operates you, and all of it is learnable in an afternoon.