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Skill

applying-optimistic-locking

Apply when creating, refactoring, changing, planning (plan mode) or reviewing repository methods that save entities with optimistic locking.

From kotlin-patterns
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$
npx claudepluginhub allousas/claude-code-plugins --plugin kotlin-patterns
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This skill uses the workspace's default tool permissions.

Supporting Assets
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examples.md
Skill Content

Purpose

Prevent lost updates when multiple processes modify the same entity concurrently. Each entity carries a version field that is checked during updates - if the version has changed since the entity was read, the update is rejected.

Typical Flow

  1. Entity includes a version field (integer, starting at 0)
  2. Repository reads entity with current version
  3. Application service performs domain operations on the entity
  4. Repository saves entity with WHERE version = ? condition
  5. If no rows are updated (version mismatch), throw OptimisticLockingException
  6. Caller decides retry strategy (controller retries, consumer relies on Kafka retry)

Guidelines

DO:

  • Add a version: Long field to entities that can be concurrently modified
  • Let version increment to 0 automatically when creating a new entity
  • Use WHERE version = ? in UPDATE/INSERT ON CONFLICT SQL statements
  • Throw a specific OptimisticLockingException when zero rows are affected
  • Increment version in the SQL statement itself (version = version + 1 or version = EXCLUDED.version + 1)
  • Keep the version check inside the repository - callers should not manage versions

DON'T:

  • Increment the version in application code - let the database handle it
  • Silently ignore zero affected rows - always throw to signal the conflict
  • Use optimistic locking on entities that are rarely modified concurrently (unnecessary complexity)
  • Retry indefinitely - set a maximum retry count

Examples

Please use always these examples as reference: examples.md

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Last CommitFeb 24, 2026
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