Doh, I had a draft reply all written up for you and never posted it. Here it is!
Delayed read replicas are your best bet, and what we suggest. We don’t do this automatically, but you can configure one cluster to be a delayed read replica of a second cluster. This would make a good doc! Stolon includes some settings for creating clusters that are delayed replicas of other clusters, you can probably run two Fly.io Postgres apps in this config: stolon/standbycluster.md at master · sorintlab/stolon · GitHub
Our long term goal is to “give” Postgres to a company like Supabase that is focused on a really nice dev UX for postgres itself. The launch story would be the same, but their tooling would handle things like point in time restores, forks, etc. You can use them right now with Fly apps, if you want.
The plumbing we build is meant to be general purpose. We’ve made it easy to create Postgres, but probably won’t ship Postgres specific infrastructure. We will be exposing volume snapshot settings soon, though. And potentially incremental volume snapshots.