Tell me about MVCC (Multi-Version Concurrency Control).

MVCC (Multi-Version Concurrency Control) is a method of managing concurrent access to data in database management systems (DBMS). The main idea of MVCC is to store multiple versions of data to enable concurrent reading and writing without locks, thereby increasing performance and reducing conflicts.

How it works:

• When reading, a transaction sees a snapshot of the data at the start of its work (its version).
• When writing, a new version of the record is created without blocking reads by other transactions.
• Old versions are kept until all transactions that can see them are completed.

Advantages of MVCC:

• No locks during reading, which improves concurrency.
• Increased performance in systems with a high number of read operations.

Example: PostgreSQL uses MVCC to ensure transaction isolation, allowing multiple users to read and modify data simultaneously without mutual locks.