US-401: Event Schema Version Governance

1. Story Title

Govern versioning & validation for analytics/domain event schemas

2. Context / Background

Events evolve; without governance consumers may break or misinterpret payloads.

3. User Persona

Primary: Data Engineer (consumer) Secondary: Platform Engineer (publisher)

4. Problem Statement

Uncontrolled changes cause downstream ETL failures & inconsistent analytics.

5. Desired Outcome

Introduce version registry, validation pipeline, and deprecation process ensuring safe schema evolution.

6. Business Value

Reduces data incidents; accelerates analytics development; builds trust in telemetry.

7. Scope (In / Out)

In: schema registry (file + version metadata), compatibility checks (additive vs breaking), CI validation step. Out: Automated consumer notification emails, full schema diff visualization UI.

8. Acceptance Criteria (BDD)

Scenario: Register new event version
  Given an existing v1 schema
  When additive field added
  Then version increments to v2
  And registry updated

Scenario: Breaking change blocked
  Given removal of required field
  When CI validation runs
  Then build fails with compatibility error

Scenario: Deprecate old version
  Given v1 superseded by v3
  When deprecation window passes
  Then v1 marked deprecated
  And warning emitted on usage

Scenario: Consumer contract validation
  Given consumer expects v2
  When publisher emits v3 event
  Then compatibility shim invoked (if backward-safe)

9. UX Notes / References

Registry Markdown table + JSON Schemas; CI output logs for failure reasons.

10. Data / Domain Model Impact

Add schema registry metadata file; no DB changes.

11. NFR Touchpoints

• Reliability: prevents silent data corruption.
• Observability: log events for version mismatch.
• Performance: validation step runs < 5s in CI.

12. Dependencies

Event publisher; analytics emitter; queue infrastructure; upcoming JSON Schemas.

13. Risks & Mitigations

Risk	Impact	Probability	Mitigation
Overly strict blocking iteration	Slow delivery	Medium	Allow experimental flag for new events
Missing backward compatible path	Consumer breakage	Low	Provide fallback adapter guidelines

14. Estimation Support

1. Registry format
2. Compatibility rules
3. CI integration
4. Deprecation policy docs

15. Analytics / Success Metrics

Version adoption curves; number of blocked breaking attempts; consumer incident rate.

16. Rollout / Release Strategy

Introduce governance for new events; migrate existing to v1 baseline.

17. Definition of Ready Checklist

• Compatibility rule set agreed

18. Definition of Done Checklist

• CI failing on breaking changes
• Registry published
• Docs updated (events-schema)

19. Open Questions

1. Enforce semantic versioning vs simple integer?
2. Provide automated changelog generation?

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Version: 1.0