IaC is awesome ๐ lemm.ee is deployed using Terraform.
My lemmy_server redundancy is mostly just so I can do infra changes without downtime (just take one node out of the load balancer, redeploy it and put the new one in), but it does also help a bit with general performance. I agree it's not strictly necessary, the vast majority of other instances are just running on a single server, but I do think it's very nice to have.
For back-ups, I have point-in-time recovery, so I can restore the database to any random timestamp - and it has actually come in useful once already when two weeks ago I was able to restore to a good state about a few minutes after a problem - I think nobody even noticed that anything happened in that case ๐