Event-Driven Microservices Architecture

Loosely-coupled microservices communicating through Kafka with dead letter queue handling and idempotent consumers.

Services

• API Gateway (api_gateway) — Accepts and validates incoming API requests — Kong, NGINX
• Order Service (service) — Manages order creation and state transitions — Java, Spring Boot
• Inventory Service (service) — Manages stock levels and reservations — Go
• Notification Service (service) — Sends notifications on order events — Python
• Kafka (queue) — Central event bus for inter-service communication — Apache Kafka
• Dead Letter Queue (queue) — Stores failed messages for retry and inspection — Apache Kafka
• PostgreSQL (database) — Stores order and inventory data — PostgreSQL
• Redis (database) — Caches inventory counts for fast lookups — Redis

Connections

• API Gateway → Order Service (sync_http)
• Order Service → Kafka (async_event)
• Kafka → Inventory Service (async_event)
• Kafka → Notification Service (async_event)
• Kafka → Dead Letter Queue (async_event)
• Order Service → PostgreSQL (db_access)
• Inventory Service → PostgreSQL (db_access)
• Inventory Service → Redis (db_access)