If more than one Endpoints API client accesses the same data at the same time, a simple locking mechanism prevents them from overwriting each other's data. When you GET an object such as an endpoint, resource, or category, the object features a lockVersion integer member that identifies the most recent modification. When you modify and PUT back the object, the request fails if the lockVersion no longer matches that of the stored version of the object, which updates when someone else modifies the data. In that case, repeat the process of reading, modifying, and writing the object back.