What is the primary benefit of Multi-Version Concurrency Control (MVCC) in databases?

• A. It eliminates the need for transaction isolation.
• B. It allows readers to access old versions while writers update, reducing locking.
• C. It prevents replication across nodes.
• D. It enforces serial execution of all transactions.

Answer: (B)

MVCC works by versioning data so that every transaction sees a consistent snapshot of the database. The benefit is that readers can access older versions while writers update, which minimizes locking and lets reads and writes proceed concurrently. In practice, a write creates a new version of the data, while existing readers continue to view the version that was current when their transaction started. This separation reduces contention, improves throughput for read-heavy workloads, and avoids blocking reads when writes are occurring. Over time, the old versions are cleaned up once they’re no longer needed, keeping the storage footprint in check.