MVCC

Databricks · Apr 21, 2026

Concurrency Control in DBMS: How Locking, MVCC and Optimistic Strategies Keep Data Consistent

The guide explains how database management systems coordinate simultaneous transactions to preserve consistency and serializability, preventing dirty reads, lost updates, non-repeatable reads and phantom reads. It compares lock-based control, including shared and exclusive locks and two-phase locking, with MVCC, which gives transactions consistent snapshots and lets readers and writers proceed without blocking. The discussion covers pessimistic and optimistic strategies, isolation levels, deadlocks, retries, lock-granularity trade-offs and MVCC’s storage and garbage-collection costs, including PostgreSQL’s VACUUM. For lakehouse workloads, Delta Lake uses a read-validate-commit process with optimistic concurrency, snapshot isolation and conflict detection for concurrent writes. The source presents Databricks Lakebase as a managed implementation offering optimistic concurrency control, snapshot isolation for reads and write-serializable isolation for writes without lock or deadlock management.