I don't think it's possible with ANY set up. All you get is that some replicas are more outdated than others. But they won't return 2 conflicting states when ReplicaA says tx1 wrote (but not tx2), while ReplicaB says tx2 wrote (but not tx1). Which is what Long Fork and Parallel Snapshot are about.
So Amazon Multi-cluster seems to replicate changes out of order?
- User1 comments
- User2 comments
- User1 checks (in a separate tx) that there's only 1 comment, so User1 gets the badge
- User2 checks the same (in a separate tx) and also sees only 1 comment (his), and also receives the badge.
With Snapshot isolation this isn't possible. At least one of the checks made in a separate tx would see 2 comments.
The original article on the Parallel Snapshot is a good read: https://scispace.com/pdf/transactional-storage-for-geo-repli...