Introduction to REST APIs

Welcome to the Interactive REST API Design course! In this course, you'll master the principles and best practices for designing clean, intuitive, and scalable RESTful APIs.

What is an API?

An API (Application Programming Interface) is a contract between two software systems that defines how they communicate. Think of it as a waiter in a restaurant: you (the client) tell the waiter what you want, and the waiter brings back your order from the kitchen (the server).

What is REST?

REST (REpresentational State Transfer) is an architectural style for designing networked applications. It was defined by Roy Fielding in his 2000 doctoral dissertation.

REST is not a protocol or standard - it's a set of architectural constraints. When a web service follows these constraints, we call it "RESTful."

Key Concepts

Resources

In REST, everything is a resource. A resource is any information that can be named:

• A user account
• A blog post
• An order
• A product catalog

Resources are identified by URIs (Uniform Resource Identifiers):

https://api.example.com/users/123
https://api.example.com/products
https://api.example.com/orders/456/items

Representations

When you request a resource, you don't get the resource itself - you get a representation of it. This is typically JSON:

{
  "id": 123,
  "name": "John Doe",
  "email": "john@example.com"
}

Statelessness

Each request must contain all the information needed to process it. The server doesn't store client context between requests.

Why REST?

REST has become the dominant approach for web APIs because:

1. Simplicity - Uses standard HTTP methods and status codes
2. Scalability - Stateless design enables horizontal scaling
3. Flexibility - Can return data in multiple formats (JSON, XML, etc.)
4. Independence - Client and server can evolve separately
5. Visibility - Requests are self-descriptive and cacheable

A Simple Example

Here's what a REST API interaction looks like:

Request:

GET /api/users/123 HTTP/1.1
Host: api.example.com
Accept: application/json

Response:

HTTP/1.1 200 OK
Content-Type: application/json

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

Exercise: Identify the Resource

Look at these URIs and identify what resource each one represents:

What You'll Learn

In this course, you'll master:

• REST architectural constraints
• Resource naming conventions
• HTTP methods (GET, POST, PUT, PATCH, DELETE)
• Status codes and error handling
• Request and response design
• Query parameters, filtering, and pagination
• Authentication strategies
• API versioning
• Documentation with OpenAPI
• Security best practices
• Testing strategies

Let's begin your journey to becoming a REST API design expert!