REST and API Design Guide

Table of Contents

• What is REST?
• Core REST Principles
• REST API Design Best Practices
• Backend System Design Roadmap
• Learning Resources

What is REST?

REST (Representational State Transfer) is an architectural style for distributed hypermedia systems, defined by Roy Fielding in 2000. It's not a protocol but a set of constraints for designing networked applications.

Core REST Principles

1. Client-Server Architecture

• Separation of concerns: Client handles UI, server handles data/storage
• Independence: Client and server can evolve independently
• Scalability: Server can be scaled without affecting clients

2. Statelessness

• No session state: Every request must contain all information needed
• Self-contained requests: Server doesn't store client context
• Benefits: Simplified scaling, reliability, and visibility

3. Cacheability

• Explicit cache control: Responses define cache policies
• Performance: Reduces server load and latency
• Cache headers: Cache-Control, ETag, Last-Modified

4. Uniform Interface

• Resource identification: URIs identify resources
• Multiple representations: JSON, XML, etc.
• Self-descriptive messages: Includes metadata in HTTP headers
• HATEOAS: Responses contain links to possible next actions

5. Layered System

• Hierarchical architecture: Load balancers, proxies, gateways
• Transparency: Client doesn't know about intermediaries
• Scalability: Each layer can be scaled independently

6. Code on Demand (Optional)

• Server executable code: JavaScript, applets
• Rarely used in modern systems

REST API Design Best Practices

Resource Naming Conventions

# Good: Use nouns, not verbs
GET /users          # Get all users
GET /users/123      # Get specific user
GET /users/123/orders  # Get user's orders

# Bad: Avoid verbs
GET /getAllUsers
GET /getUserById/123

HTTP Methods

Method	Description
GET	Retrieve resource representation
POST	Create new resource
PUT	Replace resource entirely
PATCH	Partial resource update
DELETE	Remove resource

Status Codes

Success (2xx)

• 200 OK - Request succeeded
• 201 Created - Resource created
• 204 No Content - Success, no response body

Redirection (3xx)

• 301 Moved Permanently
• 304 Not Modified

Client Errors (4xx)

• 400 Bad Request
• 401 Unauthorized
• 403 Forbidden
• 404 Not Found
• 409 Conflict
• 422 Unprocessable Entity

Server Errors (5xx)

• 500 Internal Server Error
• 502 Bad Gateway
• 503 Service Unavailable

URL Design Patterns

Collections

GET    /api/v1/products
POST   /api/v1/products

Specific Resources

GET    /api/v1/products/123
PUT    /api/v1/products/123
DELETE /api/v1/products/123

Nested Resources

GET    /api/v1/users/456/orders
POST   /api/v1/users/456/orders
GET    /api/v1/users/456/orders/789

Query Parameters

# Filtering and sorting
GET /api/v1/products?category=electronics&price_min=100&sort=price_asc

# Pagination
GET /api/v1/products?page=2&limit=20&offset=20

# Field selection
GET /api/v1/products?fields=id,name,price

Request/Response Examples

Request Body

// POST /api/v1/users
{
  "name": "John Doe",
  "email": "john@example.com",
  "age": 30
}

Response Structure

{
  "data": {
    "id": 123,
    "name": "John Doe",
    "email": "john@example.com"
  },
  "meta": {
    "timestamp": "2024-01-15T10:30:00Z",
    "version": "v1"
  }
}

Collection Response

{
  "data": [...],
  "pagination": {
    "page": 1,
    "limit": 20,
    "total": 150,
    "hasNext": true
  }
}

Error Response

{
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid email format",
    "details": {
      "field": "email",
      "value": "invalid-email"
    }
  }
}

Security Best Practices

Authentication Methods

• JWT (JSON Web Tokens): Stateless authentication
• OAuth 2.0: Third-party authorization
• API Keys: Simple authentication for public APIs
• Basic Auth: Simple username/password (HTTPS required)

Security Headers

Content-Security-Policy: default-src 'self'
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
Strict-Transport-Security: max-age=31536000

API Versioning

Path-based

/api/v1/users
/api/v2/users

Header-based

GET /users
Accept: application/vnd.api+json;version=1

Query Parameter

GET /users?version=v1

Backend System Design Roadmap

Phase 1: Fundamentals

• REST API Design
• HTTP Protocol (HTTP/1.1, HTTP/2, HTTP/3)
• Data Formats (JSON, XML, Protocol Buffers, MessagePack)

Phase 2: Core Backend Concepts

1. Database Design

   • Relational (PostgreSQL, MySQL)
   • NoSQL (MongoDB, Redis, Cassandra)
   • Indexing and query optimization
   • Transactions and ACID properties

2. Authentication & Authorization

   • JWT, OAuth 2.0, OpenID Connect
   • Session management
   • Role-based access control (RBAC)

3. Caching Strategies

   • In-memory caching (Redis, Memcached)
   • CDN caching
   • Cache invalidation patterns
   • Cache-aside, write-through, write-behind

4. Message Queues

   • Asynchronous processing
   • RabbitMQ, Apache Kafka, AWS SQS
   • Publisher-subscriber patterns
   • Event-driven architecture

Phase 3: Scalability & Performance

1. Load Balancing

   • Horizontal vs vertical scaling
   • Load balancing algorithms
   • Health checks and failover

2. Microservices Architecture

   • Service decomposition
   • Inter-service communication
   • Service discovery
   • API gateways

3. Database Scaling

   • Read replicas
   • Sharding
   • Connection pooling
   • Database clustering

4. Performance Optimization

   • Query optimization
   • Connection management
   • Resource pooling
   • Async programming

Phase 4: Advanced Topics

1. System Reliability

   • Circuit breakers
   • Retry patterns
   • Rate limiting
   • Backpressure

2. Monitoring & Observability

   • Logging, metrics, tracing
   • Application performance monitoring (APM)
   • Distributed tracing
   • Alerting systems

3. Security

   • API security (OWASP API Security)
   • DDoS protection
   • Input validation and sanitization
   • Encryption (TLS/SSL)

4. DevOps & Deployment

   • Containerization (Docker, Kubernetes)
   • CI/CD pipelines
   • Infrastructure as Code
   • Cloud platforms (AWS, GCP, Azure)

Phase 5: Specialized Topics

1. GraphQL vs REST
2. WebSocket APIs
3. Serverless Architecture
4. Edge Computing
5. API Management Platforms

Learning Resources

Books

• "Designing Data-Intensive Applications" by Martin Kleppmann
• "Building Microservices" by Sam Newman
• "RESTful Web APIs" by Leonard Richardson
• "System Design Interview" by Alex Xu

Practical Projects

1. Build a REST API with proper error handling and validation
2. Implement caching with Redis
3. Create a microservices-based application
4. Design a system with message queues
5. Build a system with real-time notifications

Next Steps

Start with database design and authentication patterns as they're fundamental to most backend systems. Then move on to caching and message queues for understanding how to build scalable systems.