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Data & Analytics · Advanced

Pessimistic Concurrency Control

A strategy that locks data when it is read for update, preventing conflicts by making others wait.

Definition

Pessimistic control, such as SELECT ... FOR UPDATE, guarantees no conflicting writes but reduces concurrency and risks blocking and deadlocks. It suits high-contention resources such as seat booking.

Example

SELECT * FROM Seats WHERE SeatID = 12 FOR UPDATE;

Exam tip

FOR UPDATE / UPDLOCK is pessimistic; version checks are optimistic.

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