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Capstone: E-Commerce Platform

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The Architecture

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Microservices

1. Product Service: Catalog management (PostgreSQL).
2. Order Service: Order placement (PostgreSQL).
3. Inventory Service: Stock checks (MySQL).
4. Notification Service: Sends emails (Simulated).

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Infrastructure

• Discovery: Netflix Eureka.
• Gateway: Spring Cloud Gateway.
• Messaging: Kafka / RabbitMQ.
• Tracing: Zipkin.

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The Flow

1. User places an order (POST /api/orders).
2. Order Service receives request.
3. Synchronous call (WebClient) to Inventory Service to check stock.
   • If out of stock -> Return 400.
4. Order Service saves order to DB (Status: PLACED).
5. Order Service publishes OrderPlacedEvent to Kafka.
6. Notification Service listens to OrderPlacedEvent and sends email.
7. Inventory Service listens to OrderPlacedEvent and reduces stock.

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Requirements

1. Service Discovery: All services must register with Eureka.
2. Gateway: All external calls must go through port 8080 (Gateway).
3. Circuit Breaker: If Inventory is down, Order Service should return a fallback (“System busy, try later”) instead of hanging.
4. Distributed Tracing: I should be able to see the trace from Gateway -> Order -> Inventory.

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Setup Instructions

1. Create a parent maven project (pom type).
2. Create modules for each service.
3. Use docker-compose to spin up the databases and brokers.
4. Implement one service at a time.
5. Test using Postman.

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Bonus Challenges

• Security: Add Keycloak (OAuth2) to the Gateway.
• Config: Move all application.yml to a Config Server.
• Resilience: Add Rate Limiting to the Order API.