A Simple Analogy

Microservices are like a restaurant. Instead of one giant kitchen doing everything, you have separate stations: grill, pastry, sauce. Each team works independently, can innovate quickly, and scales its own setup. If the grill is busy, you add more grill stations without affecting pastry.

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What Are Microservices?

Microservices is an architectural approach where applications are built as small, independent services that communicate over networks. Each service handles a specific business capability.

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Why Use Microservices?

• Scalability: Scale specific services independently
• Technology flexibility: Different services use different tech stacks
• Faster deployment: Deploy services independently without full app release
• Fault isolation: One failing service doesn't crash the system
• Team autonomy: Teams own their services end-to-end

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Monolith vs. Microservices

| Aspect | Monolith | Microservices | |--------|----------|---------------| | Deployment | All or nothing | Individual services | | Scaling | Entire app | Specific service | | Technology | Unified stack | Diverse stacks | | Development | Slower iteration | Faster innovation | | Complexity | Lower operational | Higher operational |

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Service Boundaries

User Service          Order Service         Payment Service
- Register            - Create order        - Process payment
- Login               - List orders         - Refund
- Profile             - Cancel order        - History
      |                     |                      |
      └─── API Gateway ─────┴──────────────────────┘
                     (Routes requests)

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Communication Patterns

Synchronous (HTTP/REST)

// Order Service calls Payment Service
var response = await _httpClient.PostAsync(
    "https://payment-api/process",
    new { OrderId = "123", Amount = 99.99 });

Asynchronous (Message Queue)

// Order Service publishes event; Payment Service subscribes
await _messageBus.PublishAsync(new OrderCreatedEvent 
{ 
    OrderId = "123" 
});

// Payment Service listens
public class OrderCreatedEventHandler
{
    public async Task HandleAsync(OrderCreatedEvent @event)
    {
        // Process payment async
    }
}

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Practical Example

Product Catalog       Shopping Cart        Inventory
- GetProduct()        - AddToCart()        - CheckStock()
- ListProducts()      - GetCart()          - ReserveItem()
- UpdatePrice()       - Checkout()         - UpdateStock()

Each service:
- Has its own database
- Scales independently
- Deployed separately
- Managed by different team

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Challenges and Solutions

| Challenge | Solution | |-----------|----------| | Distributed transactions | Saga pattern, event sourcing | | Data consistency | Eventual consistency | | Debugging | Distributed tracing, logging | | Network latency | Caching, async messaging |

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Related Concepts to Explore

• API Gateway pattern
• Service discovery
• Circuit breaker pattern
• Distributed tracing
• Container orchestration (Kubernetes)
• Event sourcing and CQRS

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Summary

Microservices enable building scalable, resilient systems with independent services. Master service boundaries, communication patterns, and deployment strategies to architect cloud-native applications effectively.