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Part 1: Foundations of Microservices

1.1 Introduction to Microservices

🚀 What is Microservices

Microservices is an architectural style where an application is broken down into a collection of small, autonomous services, each responsible for a specific business capability.

Each microservice:

  • Runs in its own process.
  • Is independently developed, deployed, and scaled.
  • Communicates with other services via lightweight protocols like HTTP/REST, gRPC, or messaging (e.g., Kafka, RabbitMQ).

✅ When to Use Microservices?

Use Microservices when:

  • Your application is large and complex.
  • You want to enable independent team development and deployment.
  • Different parts of your system have different scaling needs.
  • You want to improve fault isolation — failure in one service doesn't crash the whole system.
  • You're adopting DevOps, CI/CD, containerization (Docker), or cloud-native development.
  • You have long release cycles or tight coupling in your monolithic system.

❌ Avoid Microservices When:

Avoid Microservices if:

  • Your application is small or simple.
  • Your team is small — microservices add operational overhead.
  • You don’t have solid DevOps, CI/CD, monitoring, and automation in place.
  • You need tight consistency across components (microservices prefer eventual consistency).
  • You're not ready to handle complex inter-service communication and distributed system challenges.
  • You need to move fast early in development — monoliths are faster to build initially.

microservice (source:https://learn.microsoft.com/en-us/azure/architecture/guide/architecture-styles/microservices)

🧠 Key Differences: Architecture Pattern vs Design Pattern vs Architecture Style

Concept Definition Scope Example(s)
Architecture Style A broad, high-level approach to organizing a system's structure. System-wide Layered, Client-Server, Microservices, Serverless
Architecture Pattern A solution template for organizing components and their interactions in a system. High-level structure Clean Architecture, Onion Architecture, Hexagonal (Ports & Adapters), Event-Driven
Design Pattern A reusable solution to common problems in object-oriented design. Code-level Singleton, Factory, Strategy, Mediator, Repository

microservice (source:https://www.codeproject.com/Articles/5273373/Whiteapp-ASP-NET-Core-using-Onion-Architecture)

🔍 Simple Explanation:

  • Architecture Style is like the blueprint theme for your building (e.g., colonial, modern).
  • Architecture Pattern is the layout inside the building (where the rooms and walls go).
  • Design Pattern is about the furniture arrangement and how parts inside a room interact.

🧩 When to use each?

  • Use Architecture Styles to choose your system structure (e.g., microservices vs monolith).
  • Use Architecture Patterns to organize services and modules (e.g., clean separation of concerns).
  • Use Design Patterns to solve specific coding problems (e.g., reduce coupling between objects).

🏗️ Monolith vs Microservices

Aspect Monolithic Architecture Microservices Architecture
Definition A single, unified application where all components are tightly coupled. An application built as a collection of small, independent services.
Deployment Entire application is deployed together. Each service is deployed independently.
Scalability Scales as a whole unit. Individual services can be scaled independently.
Development Easier to develop initially, especially for small teams. Allows parallel development by different teams.
Technology Stack Typically uses a single stack (e.g., .NET, Java). Services can use different stacks (polyglot).
Communication Function/method calls within one app. Lightweight protocols (HTTP, REST, gRPC, messaging).
Data Management Often uses a single shared database. Each service owns its own database (database per service).
Testing Easier to test end-to-end. Requires service-level testing, mocking, integration testing.
Maintenance Can become hard to maintain as the codebase grows. Easier to maintain and update individual services.
Failure Isolation A bug in one part can crash the whole system. Failure in one service doesn’t affect others (better resilience).
Deployment Speed Slower, entire app must be redeployed for changes. Faster, deploy only the changed service.
Best For Small to medium applications or early-stage projects. Large, complex, or enterprise systems requiring scalability.

moolithic

🧠 Summary:

  • Use Monolith when you're building something simple, fast, or in the early stage.
  • Use Microservices when your system grows, and you need scalability, team independence, and faster deployments.