Optimistic Concurrency Control

A shared reading-list editor should be able to save without silently replacing someone else's work. Holding a database lock while the user thinks is impractical, but accepting every stale save is unsafe for collaboration.

Optimistic concurrency control lets the user edit freely and checks the relevant state when saving.

This chapter builds that contract from HTTP validators through atomic storage updates, then explains how clients recover when their assumptions no longer hold.