Imported from ziggkaizen/antigravity-plugin-directory (plugins/postgresql-18/skills/postgresql-18-concurrency-review/SKILL.md). Install upstream with npx skills add ziggkaizen/antigravity-plugin-directory --skill postgresql-18-concurrency-review. Copyright stays with the author (MIT).

PostgreSQL 18 Concurrency Review

Use this skill for critical state transitions, replay defense, idempotency, uniqueness, retry behavior, duplicate submissions, row/advisory locks, queue consumers, and outbox/inbox workflows.

Start Here

1. Identify the state transition and invariant.
2. Identify concurrent actors and retry sources.
3. Identify the database constraints that enforce correctness.
4. Identify the transaction boundary and isolation level.
5. Use supporting files:
   • resources/concurrency-and-replay-checklist.md
   • resources/transaction-isolation-guide.md
   • examples/idempotency-and-uniqueness-patterns.md
6. Run scripts with --help before using them:
   • scripts/postgresql-18-transaction-pattern-check.sh

Review Principles

• Prefer database constraints for invariants.
• Avoid read-check-write races.
• Use INSERT ... ON CONFLICT, unique constraints, exclusion constraints, row locks, advisory locks, or serializable transactions when appropriate.
• Design retries as part of the behavior, not as an afterthought.
• Use idempotency keys for externally retried operations.
• Keep transactions short.
• Coordinate external side effects through outbox/inbox patterns.
• Test concurrent cases, not only single-threaded behavior.

Workflows

Use workflows/concurrency-review-workflow.md for concurrency-sensitive PostgreSQL 18 changes.

Expected Output

For concurrency tasks, provide:

• Invariant and race-risk summary.
• Transaction boundary and isolation recommendation.
• Required constraints/indexes.
• Retry/idempotency/replay behavior.
• Test plan for concurrent execution.