Event Implementation Standard

Purpose

The Event Implementation Standard defines how the backend should implement internal event coordination while preserving Spring Boot Modulith boundaries.

Event Types

Type	Standard
Domain event	Produced by owning domain behavior.
Application event	Produced by use-case coordination.
Integration event	Produced at an external boundary.
Outbox event	Persisted event record for reliable publication.

Rules

• Event names are past tense.
• Source modules publish their own events.
• Consumers are idempotent.
• Events include tenant, organization, actor, correlation, causation, source, and version metadata where applicable.
• Outbox is used for events requiring reliable delivery.
• Consumers must not mutate publisher-owned facts.
• Event handlers must be small and route behavior to owning application services.

Event Flow

sequenceDiagram
    participant App as Application Service
    participant Domain
    participant Outbox
    participant EventBus as Internal Event Bus
    participant Consumer

    App->>Domain: Execute behavior
    Domain-->>App: Event fact
    App->>Outbox: Persist when reliable delivery required
    App->>EventBus: Publish internally
    EventBus->>Consumer: Deliver event
    Consumer->>Consumer: Process idempotently

Testing Expectations

Event tests verify publication, metadata, outbox persistence where required, idempotent consumption, and no source-ownership violations.