Event-Driven Communication

Services publish domain events when important business facts happen.

events

Detailed Description

Events describe facts that already happened. Subscribers decide what to do with those facts.

Use stable event contracts and versioning because events become shared integration APIs.

OrderService emits OrderPlaced
EmailService reacts
InventoryService reacts
AnalyticsService reacts

Pros

Very low coupling, easy to add subscribers

Cons

Harder to trace, duplicate events, eventual consistency

Examples: Kafka events, EventBridge, Node EventEmitter