Leave Event Idempotency and Ordering

Summary

Event identity exists end to end, but duplicate/stale handling differs by consumer and no global ordering guarantee is implemented.

Audience

Developers, QA, architects, reliability owners, and support engineers.

Concept

Component	Duplicate behavior	Staleness/ordering behavior	Source
Leave outbox	Unique integration EventId	Oldest-first polling by occurrence time; no global stream ordering	microservices/src/leave-service/Infrastructure/LeaveDbContext.cs
EmployeeProfile consumer	Compares last profile EventId	Ignores event older than stored occurrence time	microservices/src/leave-service/Messaging/EmployeeProfileConsumer.cs
Payroll consumer	Processed-event ledger by EventId	Per-snapshot last occurrence guard	microservices/src/payroll-service/Messaging/PayrollReadModelConsumer.cs
Notification consumer	Processed-event ledger by EventId	Configurable age-based stale handling	microservices/src/notification-service/Application/NotificationDispatcher.cs
Integration Service	Processed ledger and durable failure model	Does not subscribe to Leave events	microservices/src/integration-service/Domain/IntegrationEntities.cs

Leave mapping creates a new integration identity rather than retaining the domain-event identity. Correlation is set by Leave mapping; causation is absent. Tenant/business references are contract fields, but no broker partition/order key guarantee is proven.

Decision and balance events can arise from separate saves. Publication retry and competing consumer timing can expose them independently. Consumer logic must not assume request, decision, and balance events arrive as one atomic ordered group. Employee projection’s last-event check is not a full processed-event ledger and may not suppress non-consecutive replay.

Source References

• microservices/src/leave-service/Infrastructure/LeaveDbContext.cs
• microservices/src/leave-service/Messaging/EmployeeProfileConsumer.cs
• microservices/src/payroll-service/Messaging/PayrollReadModelConsumer.cs
• microservices/src/notification-service/Application/NotificationDispatcher.cs
• microservices/src/integration-service/Domain/IntegrationEntities.cs

Related Articles

• Retry and failure handling
• Payroll integration events

See Also

• Outbox and delivery

Keywords

• Idempotency
• Event ordering
• Staleness

Revision Information

• Status: Draft
• Last reviewed: 2026-07-15
• Review cycle: Quarterly