Event-Driven Architecture

Use When

• Designing asynchronous service integration, decoupled workflows, or eventual-consistency boundaries
• Introducing event sourcing, CQRS, or saga orchestration into a SaaS platform
• Selecting a message broker (RabbitMQ vs SQS/SNS vs Kafka) and a delivery guarantee model
• Hardening an existing EDA: idempotency, outbox, DLQs, schema evolution, tenant isolation

Do Not Use When

• The interaction is strictly request/response with low latency SLOs — use REST or gRPC directly (api-design-first)
• The system has a single service and no integration partners — events add cost with no benefit
• The use case needs strong cross-aggregate transactions — reconsider bounded contexts first

Required Inputs

• Target domain (bounded contexts, aggregates, business events)