Utix: Build concurrency stress tests for critical mutation paths

[prissca]

Summary

Critical mutation paths need stress tests proving concurrent requests do not create duplicate, missing, or inconsistent records.

This issue is scoped to Utix, a ticketing and event access protocol. Contributors should account for the current stack and integration points: TypeScript, ticket issuance, transfer, redemption, event operations, fraud controls, and organizer dashboards.

Difficulty

High - 200 points

Scope

• Identify mutation paths vulnerable to concurrency issues.
• Add deterministic stress or race-condition tests.
• Document any locking, idempotency, or transaction strategy used.

Acceptance criteria

• Concurrent submissions preserve domain invariants.
• No duplicate irreversible records are created.
• Tests cover concurrent success, conflicting requests, duplicate retries, and lock timeout behavior.

Technical notes

• Keep the implementation aligned with the existing repository architecture.
• Include automated tests, fixtures, or a clear validation command.
• Update contributor-facing documentation when behavior, setup, or API contracts change.
• Do not add labels; maintainers will assign labels manually.

Pull request expectations

• Explain design decisions and tradeoffs.
• Include relevant test output, screenshots, logs, or API examples.
• Call out any migration, configuration, or deployment steps.