An API (Application Programming Interface) is a set of defined rules that allow different software applications to communicate with each other. APIs are the connective tissue of modern software — they let your website talk to payment processors, your CRM sync with your marketing tools, and your mobile app fetch data from a server.
When you log in with Google, book a flight, or get real-time shipping rates at checkout, you are using APIs.
How APIs Work
An API interaction follows a request-response pattern:
- Client (your app) sends a request to the API endpoint
- The server processes the request
- The server returns a response (usually JSON or XML data)
A simple example: a weather app sends a request to a weather API with a location. The API returns temperature, humidity, and forecast data as JSON. The app displays that data to the user.
REST APIs
REST (Representational State Transfer) is the most widely adopted API architecture. REST APIs use standard HTTP methods:
| HTTP Method | Action |
|---|---|
GET | Retrieve data |
POST | Create new data |
PUT / PATCH | Update existing data |
DELETE | Remove data |
REST APIs are stateless — each request contains all the information needed to process it. They are widely understood, well-documented, and supported by virtually every programming language and platform.
Common REST API examples: Stripe (payments), Twilio (SMS), Shopify (e-commerce), Google Maps.
GraphQL
GraphQL is an alternative to REST developed by Facebook. Instead of multiple endpoints for different resources, GraphQL exposes a single endpoint where clients query exactly the data they need.
REST problem: Fetching a user profile might return 40 fields when you only need 3.
GraphQL solution: Ask for exactly name, email, and avatar — nothing more.
GraphQL is popular for complex applications with many interconnected data types and for mobile apps where minimizing data transfer matters.
Webhooks
A webhook is an event-driven API — instead of your app polling an endpoint ("did anything change?"), the external service pushes data to your app when something happens.
Examples:
- Stripe sends a webhook when a payment succeeds or fails
- GitHub sends a webhook when code is pushed to a repository
- Shopify sends a webhook when an order is placed
Webhooks enable real-time integrations without continuous polling, reducing server load and latency.
APIs and Headless Architecture
Modern headless CMS and headless commerce architectures are entirely API-driven. Content and data live in the backend; the frontend fetches and displays it via API calls. This decoupled approach enables:
- Multiple frontends (web, mobile, kiosk) from one data source
- Faster frontend performance (only fetch what you need)
- Easier integrations with third-party tools
- Independent scaling of frontend and backend
API Security Considerations
- Authentication: Use API keys, OAuth 2.0, or JWT tokens to control access
- Rate limiting: Prevent abuse by limiting requests per time period
- HTTPS: All API traffic should be encrypted in transit
- Input validation: Sanitize all incoming data to prevent injection attacks
- Versioning: Use versioned endpoints (
/api/v1/) to avoid breaking changes
How Moydus Helps
Moydus builds custom software and web applications with robust API architectures — whether that means designing a custom REST API, integrating third-party services, or building event-driven webhook systems. We also develop e-commerce platforms that connect payment gateways, inventory systems, and fulfillment services through well-structured API layers.
Contact us to discuss your integration needs.