Pessimistic vs Optimistic Locking Explained

Pessimistic locking and optimistic locking are two strategies in concurrency control mechanisms.

Pessimistic locking is a conservative strategy that assumes frequent conflicts in concurrent access, so it acquires a lock before reading or writing data. When a transaction acquires the lock, other transactions must wait for it to release the lock before accessing the data. Pessimistic locking is suitable for scenarios with frequent concurrency conflicts, such as row-level locking in databases.

Optimistic locking is an optimistic strategy that assumes conflicts due to concurrent access are rare. It does not acquire a lock when reading data, but rather checks for any modifications by other transactions when writing data. If it detects modifications by other transactions during this check, the current transaction will rollback and retry. Optimistic locking is suitable for scenarios with minimal concurrent conflicts, such as using version numbers or timestamps to determine if data has been modified.

The pessimistic lock and optimistic lock each have their own advantages and disadvantages, the choice of which strategy to use depends on the specific business scenario and the frequency of concurrency conflicts.