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by ctapobep 410 days ago
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-repli...