Cross-Service Integration Decision Guide

For implementation details, activate the backend-message-bus skill.

Quick Decision Matrix

When to Use Message Bus

✅ Use Entity Event Bus when:

• Source service owns the data
• Target services need local copies
• Eventual consistency is acceptable
• Decoupling is important

❌ Don't use when:

• You need real-time, up-to-the-second data
• Data is only needed occasionally (use API call)
• You're accessing data within the same service

Key Principles

1. Data Ownership: Each entity has ONE owner service
2. No Shared DB: Never access another service's database directly
3. Event-Driven: Use message bus for cross-service sync
4. Idempotency: Consumers must handle duplicate messages

Implementation Steps

1. Define data ownership
2. Create message in YourApp.Shared/CrossServiceMessages/
3. Implement producer in source service
4. Implement consumer in target service
5. Handle dependencies and race conditions

→ See backend-message-bus skill for detailed patterns and code examples.