Step 1: Understand the Business Requirement

Before writing code, clarify:

• What problem does the service solve?

• What is its single responsibility?

👉 Example:
“Order Service” → only handles order creation, update, status, cancellation.

🔹 Step 2: Identify Service Boundaries (DDD)

Use Domain-Driven Design (DDD):

• Identify bounded contexts

• Avoid sharing databases between services

Example:

• User Service → user data

• Order Service → orders

• Payment Service → payments

Each service owns its own database.

🔹 Step 3: Define API Contracts

Design REST APIs first:

• Endpoints

• Request/Response

• Error codes

Example:

Use OpenAPI / Swagger for documentation.

🔹 Step 4: Choose Communication Style

• Synchronous → REST (Feign/WebClient)

• Asynchronous → Kafka / RabbitMQ (events)

Use async for:

• Notifications

• Payments

• Audit logs

🔹 Step 5: Data Management Strategy

• Database per service

• No direct DB access between services

• Use events for data sync (eventual consistency)

🔹 Step 6: Handle Failures

Use:

• Circuit Breaker (Resilience4j)

• Retry with backoff

• Timeouts

• Fallbacks

🔹 Step 7: Security

• OAuth2 / JWT

• API Gateway authentication

• Role-based access control

🔹 Step 8: Observability

• Centralized logging (ELK)

• Metrics (Prometheus)

• Tracing (Zipkin / Jaeger)

🔹 Step 9: Deployment & Scalability

• Dockerize services

• Kubernetes for orchestration

• Horizontal Pod Autoscaling (HPA)

🔹 Step 10: CI/CD

• Git → Build → Test → Docker → Deploy

• Blue-Green or Canary deployment