Consider this: you leave a comment under a post. The user who posts first deserves a "first commenter badge". Now: - User1 comments - User2 comments - User1

Consider this: you leave a comment under a post. The user who posts first deserves a "first commenter badge". Now: - 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-replicated-systems-2j5mhrj29h.pdf https://scispace.com/pdf/transactional-storage-for-geo-repli...