API: What It Is, How It Works, and the Differences Between REST, SOAP, and GraphQL

How systems communicate without human intervention

API (short for Application Programming Interface) is a fundamental component of modern software, acting as a digital intermediary. The best analogy is a waiter in a restaurant: you (the customer) cannot directly access the kitchen (server) to prepare food yourself, so you place your order with the waiter (API), who takes it to the kitchen and returns with the prepared dish (response). In technical terms, it is a set of rules that allows two separate systems to exchange data and functions in a secure, standardized manner. This process relies on a “client-server” architecture and consists of four essential stages:

• Initiating the request: The client (e.g., a mobile application) sends a request to a specific address (known as an endpoint), typically using the HTTP protocol.
• Processing on the server: The server receives the request, checks its validity, and performs the necessary actions (e.g., retrieves information from the database).
• Formulating the response: The server returns the result to the client. The response is usually provided in JSON or XML format along with an HTTP status code (e.g., 200 OK).
• Displaying the result: The client interprets the received data and presents it in a format understandable to the end user.

This allows systems to operate autonomously — a weather app updates itself, and an online store checks inventory levels without employee intervention.

REST, SOAP, and GraphQL — which standard to choose?

While all APIs perform similar functions, their structures and rules differ. Currently, three main types dominate the market, each with its specifics:

REST (Representational State Transfer)

This is the most popular standard for modern web services. REST APIs are “lightweight,” flexible, and use standard HTTP methods: GET (retrieve data), POST (create), PUT (update), and DELETE (remove). A key feature is statelessness, meaning the server does not remember any information about previous client requests; each request must contain all the necessary information to be executed.

SOAP (Simple Object Access Protocol)

This is an older, strictly regulated protocol, commonly used in large corporate environments (banks, insurance systems). SOAP uses only XML format for data exchange and is characterized by very strict security standards (e.g., WS-Security). Although it is secure and reliable, its complex structure and high data volume (known as verbose) make it slower and harder to implement than REST.

GraphQL

A modern alternative developed by Facebook in 2012. Unlike REST, where data is often scattered across multiple addresses, GraphQL has only one access point. This allows the client to specify exactly what data is needed — no more, no less. This addresses the problem of “over-fetching” data and is particularly suitable for complex systems with many interrelated data points.

How to Send Requests Using JavaScript and Python

To practically use APIs, programmers use code that “calls” the server. Here’s how it looks in popular languages:

JavaScript (Fetch API)

In modern web development, the `fetch` function allows for easy asynchronous data retrieval:

fetch('https://api.example.com/users/1')
  .then(response => response.json()) // Convert the response to an object
  .then(data => {
    console.log(data.name); // Output the retrieved name
  })
  .catch(error => console.error('Error:', error));

This code sends a request, waits for a response, converts it into a readable format, and displays the result.

Python (Requests Library)

Python is known for its simplicity, and the `requests` library is the standard for working with APIs:

import requests
response = requests.get("https://api.example.com/users/1")
if response.status_code == 200:
    data = response.json()
    print(data["name"])

Here, it checks if the server responded successfully (code 200) before processing the data. This demonstrates how easy it is to integrate external data sources into your application.

From Public Data to Complex Integrations

API technologies often remain “behind the scenes,” but they power a significant portion of the digital economy. Key areas of application include:

• Payment Processing: When you shop online, the e-commerce site does not see your bank details. It uses APIs like “Stripe” or “PayPal” that securely process the transaction and return only the confirmation.
• System Integration: Companies use APIs to connect CRM systems with accounting or logistics, thus automating processes and reducing manual errors.
• Public Data and Innovation: The “Google Maps” API allows ride-sharing apps to display maps, while weather service APIs help farmers plan their work. This fosters innovation as developers do not need to build technologies from scratch.
• Social Media Tools: Marketing agencies use APIs to analyze user behavior, automate post publishing, and monitor trends in real-time.

It is important to emphasize that the success of an API depends on quality documentation. Clear instructions on how to use the interface (e.g., using “Swagger” tools) are critical for developers to quickly and effectively integrate solutions.

How Data is Protected in an Open Environment

Since APIs often provide access to sensitive data, security is a priority. Open access without protections would be catastrophic, so several layers of security are applied:

Authentication and Authorization

Most APIs require a “digital passport.” This can be a simple API key (a unique code) or a more complex OAuth 2.0 protocol that allows the user to grant access to an application (e.g., “Log in with Google”) without revealing their password.

Data Encryption and Rate Limiting

All data traffic must be encrypted using the HTTPS (SSL/TLS) standard. Rate limiting is also applied to prevent malicious actors from “overloading” the server with thousands of requests per second (DDoS attack prevention). In enterprise-level systems (SOAP), an additional WS-Security layer is often used to ensure message integrity.