What Is a REST API? 7 Fundamentals and Use Cases

APIs (application programming interfaces) are the hidden forces that power several interactions between applications, platforms and services. They come in various forms, and REST APIs are one of them. Understanding what a REST API is is crucial for developers. They can make a huge difference in how applications and cloud services work, and knowing how to leverage them lets you create seamless experiences.

What Is an API?

An API is a set of protocols and rules created to enable applications to communicate with one another. It is a connection that allows two systems to exchange everything from data to features and functionality. 

APIs are crucial in today’s software development — they allow developers to integrate third-party services into their applications without building from scratch. Therefore, they simplify the process of combining different software, allowing them to interact in a controlled and secure manner.

For example, suppose you use an app to book a ride. The application communicates with various APIs, such as mapping services and payment gateways. This is so it provides you with real-time information and a smooth user experience. With this capacity on hand — APIs make an essential part of the online world — providing efficiency and innovation in software solutions. 

What Is a REST API?

REST stands for Representational State Transfer. A REST API is a set of guidelines and constraints for building and interacting with web services. REST APIs operate over HTTP, which is the same protocol used to power the web.

Developers create this layer around a few core principles to ensure simplicity and scalability. It allows different systems to communicate with each other by using a stateless protocol — meaning each request from a client to a server must contain all the information needed to understand and process the request. This statelessness makes REST APIs particularly scalable, as each interaction is independent and self-contained. 

What makes REST APIs especially effective is their use of standard HTTP methods, including:

• GET
• POST
• PUT
• PATCH
• DELETE

These methods enable your application to perform operations on resources whose URLs are a representation of them. For example, a GET request can retrieve data from a server, while a POST request can create new data. Each resource in a REST API is uniquely identifiable, and the API facilitates interaction with these resources in a predictable, structured manner.

Because of their flexibility, REST APIs are widely used in web development. They can optimize the functions of everything from social media platforms to e-commerce sites.

Fundamentals of REST API

REST APIs have fundamental design principles that guide their creation and usage. They must align with several of these fundamentals for it to function properly.

1. Uniform Interface

All interactions between the client and server must be consistent, predictable and standardized. This means that the API follows the same set of rules and conventions regardless of the specific application or service. For instance, the REST API should ensure a user’s email address belongs to the same URI (uniform resource identifier). This keeps everything simple, making integration between platforms easy.

2. Statelessness

Since REST APIs are stateless, each request must contain all the information needed to process it. In a stateless system, the server doesn’t store any context or session data between requests, treating each interaction as an independent, isolated transaction. 

3. Client-Server Decoupling

Client-server decoupling ensures a clear separation of concerns between the client and server. In a decoupled architecture, the client and server operate completely independently. The client is responsible for the user interface and experience, while the server handles data storage, processing and business logic. This separation is essential to allow each part of the application to update without disrupting each other. 

4. HATEOAS (Hypermedia as the Engine of Application State)

HATEOAS allows the server to guide the client through available actions using hypermedia links. Instead of the client needing to know all possible interactions in advance, the server provides these links within its responses. This ensures the API remains adaptable and reduces the need for constant client-side updates as the server evolves. 

5. Cacheability

Cacheability improves performance and scalability by allowing temporary or cached storage of responses. This can occur either on the client side or at intermediate points in the network. When a response is cacheable, the system can reuse it for subsequent identical requests. The purpose of this is to reduce the need to fetch the same data from the server repeatedly. 

6. Layered System

In a REST API, the design promotes the separation of components into distinct layers. Each layer comes with its own responsibility. This architecture allows intermediaries — like proxies and gateways — to exist between the client and server without the client needing to know about them. 

7. Code on Demand (Optional)

Rest APIs allow the server to send executable code — such as JavaScript — that the client can run. While not all REST APIs use code on demand — when implemented — it can improve functionality when needed. When the code runs on demand, it will offload processing tasks to reduce the load on the server.

Common Use Cases of REST API

REST APIs have various uses, which is one of the key advantages that they provide:

Third-Party Integrations

REST APIs enable third-party integrations, allowing different applications to interact and share data with each other. For example, Salesforce’s CRM platform offers a REST API that allows developers to access and manipulate Salesforce data using standard HTTP methods. 

These methods include GET, POST, PUT and DELETE. The gateway helps retrieve customer records, update sales information and manage leads from external apps or services.

Cloud Services

Cloud services need REST APIs to communicate with other cloud-based applications and services. Amazon Web Services (AWS) provides a set of REST APIs for its numerous cloud services, such as storage, computing and database management.

Through these APIs, developers can perform actions like provisioning new servers, managing databases or accessing storage resources programmatically. With this capability, businesses can automate their cloud infrastructure and scale resources on demand.

Web Use

Web applications with REST APIs can fetch, update and display data without requiring a full page reload, creating a smoother user experience. For instance, when you scroll through a social media feed, a REST API handles the communication between the client and the server. 

This way, it can retrieve new posts or submit your data. As a result, you get faster web applications that deliver content in real time.

Mobile Applications

REST APIs also play a role in enabling apps to communicate with servers to access data and services from the cloud. For instance, a REST API can retrieve users’ chat history if you have a messaging app. The same can occur for a mobile banking application, enabling the retrieval of account balances or fund transfers. 

What Is a REST API?

Understanding what a REST API is and how it works is crucial for anyone in software development or tech-driven businesses. REST APIs are the foundation for countless applications and services, enabling communication, integration and data exchange. They will only continue to drive connectivity and growth, making them an essential tool in any developer’s toolkit.