Microservices

1️⃣ What Are Microservices?

• Microservices is a way to build a big application as many small, independent services.

• Each service does one specific job (e.g., Orders, Payments, Inventory).

• All services talk to each other using APIs or messages.

Think of it like a restaurant:

• The kitchen, billing counter, and delivery are all separate teams, but together they run the restaurant.

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2️⃣ Key Features

• Independent Deployment: Update or restart one service without stopping others.

• Own Database: Each service can have its own database.

• Technology Freedom: One service can use SQL Server, another can use MongoDB if needed.

• Scalable: You can scale only the busy service (e.g., Orders) instead of the whole app.

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3️⃣ Why Use .NET for Microservices?

• .NET 8 (or .NET 6/7) is cross-platform (Windows, Linux, containers).

• ASP.NET Core is fast for building REST APIs.

• Great support for Docker and Kubernetes.

• Many built-in tools for security, logging, and dependency injection.

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4️⃣ Typical .NET Microservice Architecture

Client (Web / Mobile)
      |
   API Gateway  ← handles routing, security
      |
  ┌─────────┬───────────┬───────────┐
  | Order   | Payment   | Inventory |
  └─────────┴───────────┴───────────┘
      |          |           |
   Own DB     Own DB      Own DB

• API Gateway: Single entry point (e.g., Ocelot or YARP).

• Services: Each built with ASP.NET Core Web API.

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5️⃣ Communication Between Services

• HTTP/REST: Simple web APIs.

• gRPC: Faster binary communication.

• Messaging/Event Bus: RabbitMQ, Azure Service Bus, Kafka for async events.

Example:

• When an order is placed, the Order service sends an “OrderPlaced” event.

• Payment and Inventory services listen and act.

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6️⃣ Steps to Build Microservices in .NET

1. Plan Services

   • Identify business areas: e.g., Customer, Product, Order.

2. Create Each Service

   • Use dotnet new webapi to create a separate ASP.NET Core project.

3. Database Per Service

   • Add EF Core or Dapper for data access.

4. API Gateway

   • Use Ocelot to route external requests.

5. Messaging (optional but recommended)

   • Add RabbitMQ/Azure Service Bus for events.

6. Containerize

   • Create Dockerfiles, run docker-compose.

7. Deploy & Scale

   • Use Kubernetes (AKS), Azure Container Apps, or AWS EKS.

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7️⃣ Example Tech Stack

• Framework: ASP.NET Core

• Database: SQL Server / PostgreSQL / MongoDB

• Message Broker: RabbitMQ or Azure Service Bus

• Gateway: Ocelot

• Container: Docker + Kubernetes

• Monitoring: Prometheus + Grafana or Azure Monitor

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8️⃣ Advantages

• ✅ Easy to scale specific services.

• ✅ Faster deployments.

• ✅ Fault isolation—one service crash doesn’t stop others.

• ✅ Freedom to choose technology per service.

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9️⃣ Challenges

• More complex deployment.

• Need strong DevOps (CI/CD, Kubernetes).

• Service-to-service security and communication.