Litestream does a couple of things. It started as a way to continuously back sqlite files up to s3. Then Ben added read replicas – you can configure Litestream to replicate from a "primary" litestream server. It's still limited to a single writer, but there's no s3 in play. You get async replication to other VMs: https://github.com/fly-apps/litestream-base

We have a feature for redirecting HTTP requests that perform writes to a single VM. This makes Litestream + replicas workable for most fullstack apps: https://fly.io/blog/globally-distributed-postgres/

It's not a perfect setup, though. You have to take the writer down to do a deploy. The next big Litestream release should solve that, and is part of what's teased in the post.