Optimistic Locking

ELI5 — The Vibe Check

Optimistic locking assumes conflicts are rare so it does not lock the row upfront. Instead, it adds a version number to each row. When you update, it checks if the version matches what you read. If someone else changed it first, your update fails and you retry. Less locking, more retrying.

Real Talk

Optimistic locking is a concurrency control strategy that checks for conflicts at write time rather than locking rows during reads. It is implemented by adding a version or timestamp column. Before updating, the query verifies the version matches. If another transaction modified the row first, the update affects 0 rows, signaling a conflict. Used when conflicts are infrequent.

Show Me The Code

-- Check version before updating
UPDATE products
SET stock = stock - 1, version = version + 1
WHERE id = 42 AND version = 7;
-- If 0 rows updated, someone else changed it first

When You'll Hear This

"Use optimistic locking for low-conflict scenarios to avoid blocking." / "The ORM uses a version column for optimistic locking automatically."