Pattern 15 / COMMS

Event-Driven Architecture

Use this when reducing direct service coupling across a workflow.

Pressure: Reducing direct service coupling across a workflow
Mechanism: Services emit facts about what happened and other services subscribe/react without direct calls
Toll: Debugging and latency become distributed across logs, queues, and consumers

Diagram for Event-Driven Architecture — Architecture plate15

Executive brief

Event-Driven Architecture fits when reducing direct service coupling across a workflow. Mechanism: services emit facts about what happened and other services subscribe/react without direct calls. Use it for microservices owned by different teams and business processes with many side effects. The toll: debugging and latency become distributed across logs, queues, and consumers.

Use when

Microservices owned by different teams and business processes with many side effects.

Example

Checkout emits paymentauthorized and downstream services continue the workflow.

Review framing

Describe the pressure first, then the mechanism, then the cost. That keeps the design grounded.

Same pressure family

Communication Patterns

12Request-Response (Synchronous)13Message Queue (Asynchronous)14Publish-Subscribe (Pub/Sub)16Webhooks 17Server-Sent Events (SSE)18Bidirectional Streaming (WebSockets / gRPC Streaming)