Microservice Design Principles

Creating new microservices

Microservice Design Principles

Core design principles and best practices for creating well-structured microservices at FlowMart

At FlowMart, we follow a set of design principles that guide the creation of new microservices. These principles help ensure our services are maintainable, scalable, and aligned with our overall architectural vision.

1. Domain-Driven Design

Each microservice should be aligned with a specific business domain or subdomain. We follow Domain-Driven Design (DDD) principles to identify service boundaries:

Bounded Contexts

Define clear bounded contexts for each service
Maintain a separate ubiquitous language within each context
Document domain models and context maps

Example Domains at FlowMart

Domain	Description	Example Services
Order	Order processing and management	order-service, order-history-service
Inventory	Product inventory management	inventory-service, stock-management-service
Customer	Customer accounts and profiles	customer-service, authentication-service
Payment	Payment processing and refunds	payment-service, refund-service
Shipping	Shipping and logistics	shipping-service, tracking-service
Catalog	Product information management	product-service, search-service

2. Single Responsibility

Each microservice should have a single responsibility and a clear purpose:

Focus on one business capability: Services should do one thing well
Right-sized services: Not too large (mini-monolith) or too small (nano-service)
Cohesive functionality: Related functions should be grouped together

3. Data Ownership

Microservices should own their data and maintain data autonomy:

Each service has its own database or data store
No direct data sharing between services
Data is exposed through well-defined APIs
Services should be the single source of truth for their domain data

4. API Design

All FlowMart microservices must follow our API Management and Governance Strategy:

RESTful APIs

Use consistent resource naming conventions
Follow standard HTTP methods and status codes
Implement proper error handling and validation
Design for backward compatibility

Event-Driven Interfaces

Define clear event schemas using AsyncAPI
Document event ownership and responsibilities
Follow event versioning standards
Implement idempotent event consumers

5. Resilience and Fault Tolerance

Microservices must be designed to handle failures gracefully:

Implement circuit breakers for downstream dependencies
Use timeouts and retries with exponential backoff
Design for graceful degradation of functionality
Implement health checks and readiness probes

6. Observability

All services must expose monitoring and observability data:

Structured logging (using our ELK stack)
Metrics exposure (Prometheus format)
Distributed tracing support (Jaeger)
Health check endpoints

7. Security by Design

Security must be integrated into every service:

Authentication using OAuth 2.0 / OpenID Connect
Authorization using role-based access control
TLS encryption for all communications
Input validation and output encoding
No sensitive data in logs or traces

8. Testability

Services should be designed with testing in mind:

High unit test coverage (minimum 80%)
Integration tests for all critical paths
Contract tests for API interfaces
Easy local testing setup
Simulated dependencies for development

9. Configuration Management

Services should follow our configuration management approach:

Environment-specific configuration via Kubernetes ConfigMaps
Secrets management via HashiCorp Vault
Feature flags for conditional functionality
No hardcoded configuration values

10. Independence and Deployability

Services should be independently deployable:

No deployment coupling with other services
Infrastructure as Code for all resources
Self-contained CI/CD pipelines
Blue/green or canary deployment capabilities

Microservice Checklist

Use this checklist when designing a new service:

Next Steps

Learn how to create a Node.js microservice
Explore TypeScript service implementation
Understand our Terraform infrastructure modules

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