Which statement about locking strategies is true?

• A. Pessimistic locking checks for conflicts at commit time.
• B. Optimistic locking locks resources for the duration of the transaction.
• C. Pessimistic locking is preferable in high-concurrency scenarios.
• D. Optimistic locking is never suitable for low contention.

Answer: (C)

Locking strategies differ in when conflicts are prevented. Pessimistic locking locks the resource as soon as it’s accessed, so other transactions can’t modify it until you’re done. This prevents conflicting updates upfront, which is especially helpful when many processes might try to change the same data at once. Optimistic locking, on the other hand, lets multiple transactions proceed concurrently without locking and only checks for conflicts at commit time; if a conflict is detected, the transaction is retried.

In high-concurrency scenarios, pessimistic locking is preferable because the likelihood of conflicts is high, making preemptive locking a safer way to maintain consistency and avoid costly retries. The other statements mix up when the lock occurs or describe optimistic locking as never suitable for low contention, which isn’t accurate—optimistic locking is well-suited for low-contest situations where locking overhead would be wasteful.