REST API

What is REST API?

REST API (Representational State Transfer) is a standardized rule set that enables different applications to send and receive data over the internet. It leverages HTTP, the web protocol everyone knows, to achieve simple and practical data exchange. Mobile apps retrieving information from servers, websites integrating with external services, IoT devices sending data to the cloud—virtually all modern systems operate through REST APIs. By following RESTful design principles, you can build scalable, maintainable, and predictable APIs. The success of REST API lies in its widespread adoption due to “simplicity,” “scalability,” and “ease of learning.”

In a nutshell: Just as browsers load web pages, applications can simply read and write necessary data from other applications using common rules. It’s like using an address to find a book in a library—the same mechanism applies.

Key points:

• What it does: Uses HTTP protocol to enable standardized data exchange between applications
• Why it’s needed: To seamlessly connect systems built with different technologies and create scalable, maintainable systems
• Who uses it: Backend developers of web and mobile applications, API designers, system integrators
• Design principles: Stateless design, resource-oriented design, standardized operations (GET/POST/PUT/DELETE)

Why it matters

Without REST API, application development becomes extremely complex. For example, if a mobile app needs to retrieve member information, without REST API, developers would need to design their own complex communication protocol. However, with REST API as a standard, everyone can follow understandable rules: “This is data retrieval, so use GET” or “This is data update, so use PUT.”

This standardization enables systems developed by different companies to interact easily. Developers can immediately apply existing knowledge to new projects, increasing development speed and reducing errors. Following RESTful design improves code readability and maintainability, making system scaling easier.

How it works

REST API’s foundation rests on the concept of “resources.” All information in a database—users, products, orders—is treated as “resources.” Each resource is identified by a unique URL. For example, “/users/123” represents “user ID 123 data.” This resource-oriented approach enables intuitive design that makes complex operations understandable.

Communication uses four basic HTTP methods. “GET” retrieves information, “POST” creates new information, “PUT” updates information, and “DELETE” deletes information. For example, “GET /products” means “retrieve all product listings.” The “PATCH” method is used for partial updates.

The API server processes each request it receives, handling the requested resource and returning results in JSON format (or XML). Status codes (200 for success, 404 for not found, 500 for server error) communicate the request processing results. This simple exchange binds complex systems together.

An important characteristic of REST API is “stateless design.” This means the server doesn’t maintain client state, so each request is processed independently, making scaling straightforward. “Cacheability” allows GET request results to be cached, reducing network traffic and server load.

Real-world use cases

Web application backends

Frontend JavaScript constantly communicates with backend APIs for user authentication, data storage, and real-time information updates. Thanks to REST API, frontend and backend developers can work independently.

Mobile app development

iOS and Android apps can efficiently send and receive all needed information—user profiles, messages, files—through REST APIs. You can also minimize battery consumption by selecting only the information you need.

Microservices architecture

Large systems are divided into multiple small services that communicate via REST API, making development and maintenance easier. Each service is independently developed and deployed while seamlessly functioning as a whole.

Benefits and considerations

REST API’s greatest benefit is “simplicity.” It requires no complex specifications, so learning costs are low and implementation completes quickly. Caching functionality accelerates responses to identical requests and reduces server load. Stateless design enables easy horizontal scaling of servers, making it suitable for enterprise-level system construction.

Considerations include that REST’s strict constraints may make it difficult to handle complex query requirements. For instance, when retrieving information from multiple resources simultaneously, multiple API calls may be necessary (called the “N+1 problem”). Retrieving related data across multiple API calls increases communication volume. In such cases, considering GraphQL has value. However, for many use cases this simplicity becomes an advantage, so REST API will likely remain mainstream.

REST API design best practices

To design effective REST APIs, observe these principles:

1. Resource-oriented design — Design around nouns (resources), not verbs
2. Versioning strategy — Clear version management for API changes
3. Error handling — Provide appropriate status codes and detailed error messages
4. Documentation — Use standard formats like OpenAPI (Swagger) for clear documentation
5. Rate limiting — Prevent API abuse and protect server resources

Related terms

• HTTP — The basic protocol used for communication in REST APIs
• API Design — Best practices for designing effective APIs following REST principles
• Authentication and Authorization — Essential elements for ensuring REST API security
• GraphQL — An alternative to REST for handling complex queries
• API Gateway — A component for unified management of multiple REST APIs

Frequently asked questions

Q: What’s the difference between REST API and SOAP? A: REST API is simple and easy to learn, leveraging web standards. SOAP is more complex with stricter specifications, designed for enterprise systems. Modern development favors REST API.

Q: How much security does REST API provide? A: REST API itself is not a security protocol but just a communication method. Security is realized through additional layers like HTTPS, OAuth2, and API key authentication. Properly combining these is important.