What is an API, where and how to use it?

We review API architecture, protocols, and applications — how application programming interfaces connect systems and why it is important for business.

Definition and Mechanism of API

API (short for Application Programming Interface) is an essential part of modern software, acting as a digital intermediary. An API can be imagined as a waiter in a restaurant: you (the customer) cannot directly go into the kitchen (server) and cook the food yourself, so you place an order with the waiter (API), who takes it to the kitchen and returns with the prepared dish (response).

It is a mechanism that allows two separate software components to exchange data and functions in a secure, standardized way. The process is based on a “client-server” architecture and occurs in four main stages:

• Request initiation: The client (e.g., mobile app) sends a request to a specific address (English: endpoint), usually using the HTTP protocol.
• Processing on the server: The server receives the request, checks its validity, and performs the necessary actions (e.g., retrieves data from the database).
• Response formation: The server returns the result to the client. The response is usually provided in JSON or XML format along with a status code (e.g., 200 OK).
• Result representation: The client interprets the received data and presents it in a user-friendly format.

Diversity of Architectures and Protocols

Although all APIs perform a similar function, their structure and rules differ. Currently, three main types are distinguished:

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 (delete). A key feature is statelessness (English: stateless).

SOAP (Simple Object Access Protocol)

This is an older, strictly regulated protocol, commonly used in corporate environments (banks, insurance systems). SOAP uses only XML format for data exchange and features strict security standards (e.g., WS-Security).

GraphQL

A modern alternative created 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.

Programming Examples

fetch('https://api.example.com/v1') .then(res => res.json()) .then(data => console.log(data)); 

 import requests res = requests.get("api.url") if res.status_code == 200: print(res.json()) 

Real-World Application and Benefits for Business

API technologies are invisible, but they power a large part of the digital economy. Key areas of use include:

• Payment processing: Online stores use “Stripe” or “PayPal” APIs that securely process transactions.
• System integration: Companies connect CRM systems with accounting or logistics, automating processes.
• Public data: The “Google Maps” API allows other applications to display maps, while weather service APIs help plan tasks.

Security and Access Management

Since APIs often provide access to sensitive data, security is a priority. Several levels of protection are applied:

Authentication and Authorization

Most APIs require a digital passport. This can be an API key (a unique code) or the OAuth 2.0 protocol, which allows the user to grant access to the application 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 overwhelming the server with requests.