What you'd do exactly depends on your database. For Postgres you could use something like Citus, you also could setup your own duplication, but in general yeah

What you'd do exactly depends on your database. For Postgres you could use something like Citus, you also could setup your own duplication, but in general yeah setup a few VPS, setup the replicas and some load balancing and you're good. Managed DB costs can seem confusing, look at your data for egress, storage, read and writes. Most have a calculator where you can plug in the data to estimate.