I've designed our app so that there are only two stateful services that matter: Database and Disk. Everything else is cattle, you can shut down or spin up new instances and the load balancer redirects requests with no impact. Making Postgres redundant is a matter of careful configuration with PGBouncer + HAProxy + Patroni. However for a long time we had a much simpler setup: just restore a new database from backup on a new machine if the main one failed (one-time simple script run manually - not automatic, means a little bit of downtime if there's a failure, but it worked). Or you could use CockroachDB. Making disk redundant: just use MinIO for S3-like disk (that's also where DB backups are stored). You can lose up to 2 out 4 of your servers and you lose nothing.

With this setup if 1 or 2 Mac Studios fail (or need to be restarted for updates) everything just keeps running smoothly with no customer impact. It also helps that the app itself is on the Elixir BEAM (Phoenix) so everything "just works" across all machines.