RESTful API Design Principles
💡 Concept Name
RESTful API Design Principles are foundational guidelines that help create APIs that are consistent, scalable, and easy to use across platforms.
📘 Quick Intro
RESTful APIs leverage HTTP to interact with stateless resources, promoting simplicity and consistency. Following REST principles ensures APIs are easy to understand, maintain, and integrate.
🧠 Analogy / Short Story
Think of REST as a postal service: you send a letter (request) to a specific address (resource URI) with instructions (HTTP method), and expect a reply (response). The system doesn't need to remember previous letters, making communication stateless and reliable.
🔧 Technical Explanation
- 📍 Resource-Based URIs: Use clear nouns such as
/usersor/productsinstead of verbs to represent resources. - 📬 HTTP Methods: Use
GETto read,POSTto create,PUTorPATCHto update, andDELETEto remove resources. - 🧠 Statelessness: Each request must contain all necessary information; the server does not store client state.
- 📦 Representations: Data can be formatted as JSON, XML, or other types depending on client needs.
- 🔄 Idempotency: Methods like
PUTandDELETEshould have the same effect no matter how many times they are called. - 🧭 HATEOAS: Hypermedia links help clients discover available actions dynamically.
- 🔐 Authentication: Use secure standards such as OAuth2, API keys, or JWT tokens.
🎯 Purpose & Use Case
- ✅ Build scalable and interoperable APIs usable by web, mobile, and cloud applications.
- ✅ Enable third-party developers to integrate easily through clear API contracts.
- ✅ Support long-term API maintenance and evolution with consistent design.
💻 Real Code Example
// ASP.NET Core RESTful API example
[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
[HttpGet]
public IActionResult GetAll() => Ok(productService.GetAll());
[HttpGet("{id}")]
public IActionResult Get(int id) => Ok(productService.GetById(id));
[HttpPost]
public IActionResult Create(Product product)
{
var created = productService.Create(product);
return CreatedAtAction(nameof(Get), new { id = created.Id }, created);
}
[HttpPut("{id}")]
public IActionResult Update(int id, Product product)
{
productService.Update(id, product);
return NoContent();
}
[HttpDelete("{id}")]
public IActionResult Delete(int id)
{
productService.Delete(id);
return NoContent();
}
}
❓ Interview Q&A
Q1: What is a RESTful API?
A: A service that follows REST principles and uses HTTP to manage and access resources via URIs.
Q2: Why use nouns instead of verbs in API endpoints?
A: Because REST treats endpoints as resources, which are best represented by nouns.
Q3: What does statelessness mean in REST?
A: Every request is independent and contains all information needed for processing.
Q4: What does idempotency mean in REST APIs?
A: Repeating requests should not alter the result beyond the initial application.
Q5: How does HATEOAS improve REST APIs?
A: By providing links that guide clients to related resources and actions dynamically.
📝 MCQs
Q1. Which HTTP method retrieves data?
- POST
- GET
- PUT
- DELETE
Q2. What is statelessness in REST?
- No server logs
- Each request is independent
- Persistent sessions
- Clients store all data
Q3. What is a RESTful URI example?
- /getUser
- /users/123
- /api?user=123
- /show-user
Q4. Which method creates new resources?
- GET
- POST
- DELETE
- PUT
Q5. Which HTTP methods should be idempotent?
- GET and POST
- POST and DELETE
- PUT and DELETE
- Only POST
Q6. What does HATEOAS stand for?
- HTTP Asynchronous Transfer Engine
- Hypertext Architecture Template
- Hypermedia As The Engine Of Application State
- Hyper API Transition Element
Q7. What is the role of URI in REST?
- Stores data
- Handles cookies
- Identifies resources
- Authenticates users
Q8. Why are REST APIs scalable?
- Due to XML
- Because of statelessness
- Uses WebSockets
- Supports SOAP
Q9. Which response code indicates resource creation?
- 200
- 201
- 204
- 400
Q10. What is the typical format for REST responses?
- HTML
- Plain Text
- JSON
- Markdown
💡 Bonus Insight
Incorporate versioning (e.g., /v1/products), clear HTTP status codes, and descriptive error messages to build resilient and maintainable REST APIs.
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