API
Definition
API stands for Application Programming Interface. It is a set of rules and protocols that allow different software applications to communicate with each other. APIs define how requests and responses are structured, enabling developers to connect systems, services, or devices without needing to understand their internal workings.
APIs are commonly used to integrate third-party services, connect frontends to backends, and enable automation. For example, an e-commerce site may use an API to process payments, retrieve product data, or send shipping updates.
Advanced
At an advanced level, APIs can be designed using different architectures. REST APIs use standard HTTP methods such as GET, POST, PUT, and DELETE. GraphQL provides a flexible query language for fetching exactly the data needed. SOAP is a protocol-driven model often used in enterprise environments.
Modern APIs use authentication and authorisation standards such as OAuth 2.0, API keys, or JWTs. They may include rate limiting, caching, and monitoring to improve performance and security. APIs are also central to microservices and serverless architectures.
Why it matters
Use cases
Metrics
Issues
Example
A travel booking website uses multiple APIs to deliver its services. One API retrieves flight data, another handles payments, and a third manages customer reviews. By integrating these services, the company provides a seamless user experience without building every feature in-house.