# Technical Documentation: RESTful API Design Guidelines

## Introduction

This document outlines best practices for designing and implementing RESTful APIs in modern web applications. It covers HTTP methods, status codes, authentication, and data serialization.

## HTTP Methods

### GET Requests
- Used for retrieving data
- Should be idempotent
- No request body
- Cacheable by default

### POST Requests
- Used for creating new resources
- Not idempotent
- Includes request body
- Should return 201 Created on success

### PUT Requests
- Used for updating entire resources
- Idempotent operation
- Replaces entire resource
- Should return 200 OK or 204 No Content

### DELETE Requests
- Used for removing resources
- Idempotent operation
- Should return 204 No Content
- May return 404 if resource doesn't exist

## Status Codes

### 2xx Success
- 200 OK: Request successful
- 201 Created: Resource created
- 204 No Content: Success with no response body

### 4xx Client Error
- 400 Bad Request: Invalid request syntax
- 401 Unauthorized: Authentication required
- 403 Forbidden: Access denied
- 404 Not Found: Resource doesn't exist

### 5xx Server Error
- 500 Internal Server Error: Server-side error
- 502 Bad Gateway: Invalid response from upstream
- 503 Service Unavailable: Server temporarily unavailable

## Authentication

### Bearer Token Authentication
```
Authorization: Bearer <token>
```

### API Key Authentication
```
X-API-Key: <api-key>
```

## Data Serialization

### JSON Format
- Use camelCase for property names
- Include appropriate Content-Type headers
- Validate JSON schema

### XML Format
- Use clear element names
- Include proper namespaces
- Validate against XSD schema

## Conclusion

Following these guidelines ensures consistent, maintainable, and scalable API design that improves developer experience and system reliability.
