---
title: "Microservices Architecture"
description: "Design patterns and best practices for microservices"
keywords: ["microservices", "architecture", "distributed", "services"]
category: "architecture"
tags: ["microservices", "distributed-systems", "architecture"]
---

# Microservices Architecture

## Core Principles

### Single Responsibility
Each service owns one business capability:
- User service: Authentication, profiles
- Order service: Order management
- Payment service: Payment processing

### Independent Deployment
Services deploy independently without coordinating releases.

### Decentralized Data
Each service owns its database - no shared databases.

## Communication Patterns

### Synchronous (REST/gRPC)
```
User Service --HTTP--> Order Service
```
**Pros**: Simple, immediate response  
**Cons**: Tight coupling, cascading failures

### Asynchronous (Message Queue)
```
Order Service --Message--> Payment Service
```
**Pros**: Loose coupling, resilient  
**Cons**: Eventual consistency, complexity

## Service Discovery

Services register and discover each other:
- **Client-side**: Service queries registry (Consul, Eureka)
- **Server-side**: Load balancer handles routing (Kubernetes, load balancer)

## API Gateway

Single entry point for clients:
- Routes requests to services
- Handles authentication
- Rate limiting
- Request/response transformation

## Data Consistency

### Saga Pattern
Distributed transaction across services:
1. Order service creates order
2. Payment service processes payment
3. Inventory service reserves items
4. If any fails, compensating transactions rollback

### Event Sourcing
Store events, not current state:
- Append-only event log
- Rebuild state by replaying events
- Audit trail included

## Challenges

### Distributed Tracing
Track requests across services using correlation IDs.

### Monitoring
Centralized logging and metrics (ELK, Prometheus, Grafana).

### Testing
- Unit tests per service
- Integration tests for service interactions
- Contract testing for API compatibility
