⚙️ Under the Hood: How Databases Handle Multiple Users Concurrently

Short summary

Database concurrency control ensures thousands of users safely read and write simultaneously through three strategies: pessimistic locking (2PL), optimistic concurrency, and MVCC. MVCC (PostgreSQL/MySQL) creates row versions and transaction snapshots, allowing readers to see consistent database views without blocking writers. Supporting infrastructure includes buffer pools, latches, write-ahead logs for durability, and isolation levels balancing consistency with throughput.

• •Three concurrency strategies explained: pessimistic locking (2PL with deadlock detection), optimistic concurrency (read-heavy), MVCC (modern default)
• •MVCC creates row versions per transaction ID, allowing readers to see consistent snapshots without blocking writers
• •Infrastructure: buffer pools, latches, write-ahead logs for durability, isolation levels (Read Uncommitted through Serializable)

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