implement-optimistic-concurrency-control

name	implement-optimistic-concurrency-control
category	code
description	Implement optimistic concurrency control with version identity, conditional writes, conflict semantics, retries, merge policy, and user recovery. Use when concurrent updates must not silently overwrite one another.

implement-optimistic-concurrency-control

When to use

• Use where contention is bounded and lost updates are unacceptable.
• Do not automatically retry noncommutative or externally side-effecting updates.

Preconditions

• Define entity, invariants, version source, operations, conflict rate, merge authority, and clients.

Procedure

1. Choose monotonic version, ETag, compare value, or database-native token.
2. Return the version with every readable representation.
3. Require the expected version in each mutation and update atomically.
4. Return a structured conflict with current version and safe reconciliation data.
5. Retry only operations proven idempotent and commutative.
6. Test simultaneous create, update, delete, batch, stale cache, and side effects.

Failure plan

• Route semantic conflicts to explicit user or domain resolution.

Worked example

Two editors change a policy; the second write receives a conflict rather than erasing the first.

Done

• A concurrency implementation records version contract, atomic update, conflict response, retry, merge, and telemetry
• Simultaneous, stale, delete, batch, idempotency, side-effect, cache, and user-recovery tests verify correctness