RESTful API: Why Is It Still the Standard for Web APIs?

Imagine walking into a fine restaurant. You raise your hand, and a waiter comes to take your order along with your table number. The waiter delivers the request to the kitchen, and a few minutes later returns with the dish you asked for.

You don’t need to know how the kitchen works, you only care that your order arrives correctly. Meanwhile, many other waiters are serving many other tables at the same time.

If this sounds familiar, it’s because this is a common analogy used to explain how APIs work.

In the world of software, an API acts much like the waiter in this story. The client sends a request describing what it needs, the server processes that request, and then returns the result. The client does not need to understand the internal implementation of the server, only how to communicate with it.

One of the most widely used approaches for building web APIs today is the REST architecture style. REST leverages the widely adopted HTTP protocol to standardize how clients request resources and how servers respond, typically using lightweight data formats such as JSON.

Because of its simplicity, scalability, and compatibility with the web, RESTful APIs have become the de facto standard for modern web services.

What is RESTful API ?

Beginners often confuse REST with RESTful APIs due to how people casually use the term “REST API.”

To clarify:

• REST is a set of architectural principles
• RESTful API is an API that follows those REST principles In short, a RESTful API is simply an API designed according to REST constraints.

REST like a blueprint while RESTful Api is the iplementation

Principle 1: Client–Server

This is the most fundamental principle.
Client and server are separated into independent entities. This allows one or multiple servers to serve one or many clients simultaneously.
This separation decouples the user interface from the business logic, making it possible to update either side without affecting the other.

Benefits:

• Easier to maintain
• Can scale independently
• Frontend and backend teams can work separately

Principle 2: Stateless

The server does not store any previous request state.
Each request is independent and must contain all necessary information (e.g., authentication token, resource identifiers).
This makes the system more scalable and reliable because any server can handle any request.

Compare to stateful api, request depend on state of last request
Server save state of client between requests

For example:
With stateless, after login request was sent to server with all informations like token, resource.. server don't need to remember last request, it just handle current request
With stateful, after login, server need to create a session to save save your login session, if session was forget, you log out.

Benefits

• Eazy to scale
• Better performance
• Better for loadalancing ...

Principle 3: Cacheable

Server responses can be cached.
REST allows clients (apps, browsers) or intermediaries (proxies) to store responses temporarily.
Benefits:

• Reduce the number of requests to the server
• Improve response time
• Save bandwidth

Principle 4: Uniform Interface

This is the most important principle of REST.
It defines a consistent way to interact with resources.
Each resource should have a unique URL:

• Get all users → /users
• Get a specific user → /users/1

Avoid using action-based URLs like:

• /getUser
• /createUser

REST leverages HTTP methods to define actions:

• GET → retrieve data
• POST → create new data
• DELETE → remove data
• PUT → update entire resource
• PATCH → update partial resource

Resource Representation
The server does not return raw objects or database records directly.
Instead, it returns a representation of the resource, typically in formats like JSON or XML.
For example, when building a RESTful API with Spring Framework, the backend does not expose Java objects directly—it returns JSON representations.

{
"id": "8f3c2a9e-5b1d-4c7a-9f2e-1a6b3d8c4e10",
"username": "john_doe92",
"email": "[e-mail]",
"firstName": "John",
"lastName": "Doe",
"phone": "[phone]",
"dateOfBirth": "1992-06-15",
"gender": "male"
}

This standardization allows different systems to communicate consistently.

Benefits:

• Standardization comunication (commonly json/xml)
• Security (pass nessary information in request/response)
• api versioning

Principle 5: Layered System

Clients do not need to know whether they are communicating directly with the main server or through intermediaries.
In modern architectures (especially microservices), requests often pass through multiple layers:

For example:
Browser → CDN → Gateway → Load Balancer → Security → Business Service → Database
The client only needs to know the endpoint.

Benefits:

• Easier scaling
• Better maintainability
• Independent services
• Improved performance via load balancing

Principle 6: Code on Demand (Optional)

Instead of sending only data (JSON/XML), the server can send executable code for the client to run.
However, this approach is rarely used in modern APIs and is generally not recommended.

Compare to other style of API

REST is a very good style of API, but not all time we use it

With out REST, there are many style of API like GraphQL, gPRC...
Get gPRC for example, if you need a hign performance or realtime streaming
Try to compare REST and gPRC

Final Thoughts

From a developer’s perspective, REST is not a protocol but a design philosophy.
Understanding and applying these principles correctly will help you build APIs that are scalable, maintainable, and easy to use.
A RESTful API is simply the practical implementation of those ideas.