Most applications have to deal with concurrency. Concurrency is a circumstance where two users modify the same entity at the same time. There are two types of concurrency handling: optimistic and pessimistic. There is no concurrency where the last user always wins. When this happens, there is a silent data loss, where the first user's changes are overwritten without notice, so it is not frequently used. In the case of pessimistic concurrency, only one user can edit a record at a time and the second user gets an error, stating that they cannot make any changes at that time. Although this approach is safe, it does not scale well and results in poor user experience. As a result, most applications use optimistic concurrency, allowing multiple users to make changes, but checking for a concurrency situation at the time changes are being saved. At that time if two users changed the same row of data, applications issue an error to the second user, letting them know that they...