Every decision for an external dependency that a self-hosted service makes is another chance for it to have that impedance mismatch you mentioned. Postgres is

Every decision for an external dependency that a self-hosted service makes is another chance for it to have that impedance mismatch you mentioned. Postgres is a relatively uncontroversial one, but I had the benefit of working for a company already operating a production postgres cluster where I could easily spin up a new database for a service. I went with SQLite/on disk storage because for most companies, providing a resilient block storage device, with backups, is likely trivial, regardless of which cloud they're on, being on bare metal, etc.