🧩 Microservices Architecture

✅ Overview

A structural style splitting the application into small independent services, enabling independent deployment and independent scale.

✅ Problems Addressed

• Development speed slowdown of huge Monolith.
• Collision due to team scale increase.
• Response to different scale characteristics per feature.

✅ Basic Philosophy & Rules

• Independent deployment per service.
• Independent data store (Database per Service).
• Loosely coupled coordination via API (REST / gRPC / Event).
• Strong prerequisite of DevOps / CI/CD / Observability.

Conceptual Diagram

Source: Microsoft, “Microservices architecture style – Azure Architecture Center”.
https://learn.microsoft.com/en-us/azure/architecture/guide/architecture-styles/microservices

✅ Suitable Applications

• Development in multi-team / multi-domain.
• Web services with high availability / scale requirements.
• When technology selection differs per feature.

❌ Unsuitable Cases

• Small-scale products (Over-engineering).
• Heavy operation, insufficient SRE structure.
• Domains where distributed transactions occur massively.

✅ History

• Spread by success of Netflix / Amazon.
• Developed as a school implementing SOA ideas more lightly.

✅ Related Styles

• SOA: Heavier and enterprise-like ancestor.
• Modular Monolith: Effective as structural organization before introduction.

✅ Representative Frameworks

• Spring Cloud
  Comprehensive foundation for Microservices like Config / Gateway / Discovery / Circuit Breaker.

• Go + gRPC + Kubernetes
  Strong combination for building lightweight and fast services.

• Node.js / NestJS / Express
  Configuration suitable for BFF and small-grained services.

• AWS (ECS / Lambda / API Gateway / EventBridge)
  Microservices construction by managed services.

• Dapr
  Platform providing service-to-service invocation via sidecar.

✅ Design Patterns Supporting This Style

• Facade
  Unified entrance via API Gateway.

• Proxy
  Traffic control by Service Mesh or Sidecar.

• Observer
  Event-driven coordination and domain event distribution.

• Mediator
  Coordination of multiple services by Orchestrator (Workflow).

• Strategy
  Different algorithm / technology selection per service.

✅ Summary

Microservices is a powerful structure for
"High Speed Development × High Scale × High Availability",
but since operation cost is high, it depends on organizational scale and domain characteristics.