What is a Web API?
A Web API (Application Programming Interface) is a set of HTTP-based endpoints that allow systems, applications, or devices to communicate over the web.
Examples
Retrieving weather data from a weather API.
Sending payments using the Stripe API.
Fetching user data from your own backend for a mobile app.
Key features
Communicates using HTTP(S)
Returns structured data (JSON, XML, etc.)
Follows REST, GraphQL, or gRPC conventions
Enables machine-to-machine communication
Types of Web APIs
| Type | Description | Example |
|---|
| REST API | Resource-based, uses HTTP verbs (GET, POST, PUT, DELETE) | Twitter API, Shopify API |
| SOAP API | XML-based, strict contract using WSDL | Legacy banking systems |
| GraphQL API | Flexible querying, client decides what data to fetch | GitHub GraphQL API |
| gRPC API | High-performance, uses Protocol Buffers, ideal for microservices | Kubernetes API server |
| Webhooks | Event-driven callbacks sent to a URL | Stripe sends payment success event |
Core Concepts of RESTful Web API
Resources → Represented by URLs (e.g., /products/123)
HTTP Verbs →
GET = Read
POST = Create
PUT/PATCH = Update
DELETE = Remove
HTTP Status Codes
200 OK, 201 Created, 400 Bad Request, 401 Unauthorized, 404 Not Found
Statelessness → Each request is independent, no server-side session
JSON Format → Most common response payload
Web API Architecture
A typical Web API architecture includes:
Client (browser, mobile app, other service)
API Gateway / Reverse Proxy (optional, for routing & security)
Web API Layer (controllers, endpoints)
Business Logic Layer (services)
Data Access Layer (database / external APIs)
Persistence (SQL, NoSQL)
Authentication & Authorization (JWT, OAuth2)
Building a Web API (Step-by-Step)
Example: .NET Web API
Create a Project
dotnet new webapi -n ProductApi
Define Model
public class Product {
public int Id { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
}
Create Controller
[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase {
private static List<Product> _products = new();
[HttpGet]
public IActionResult GetAll() => Ok(_products);
[HttpPost]
public IActionResult Create(Product product) {
product.Id = _products.Count + 1;
_products.Add(product);
return CreatedAtAction(nameof(GetAll), product);
}
}
Run & Test
Best Practices for Web APIs
✅ Use Versioning – api/v1/products
✅ Return Proper HTTP Codes – 404 for not found, 400 for bad input
✅ Validation & Error Handling – Always return meaningful errors
✅ Pagination, Filtering, Sorting – For large datasets
✅ Rate Limiting & Throttling – Prevent abuse
✅ Caching – ETag, HTTP cache headers for performance
✅ OpenAPI/Swagger Docs – Self-documenting APIs
Security Considerations
HTTPS Only – Encrypt all traffic
Authentication
Authorization – Role-based access (RBAC)
Input Sanitization – Prevent injection attacks
CORS Policy – Restrict allowed origins
Rate Limiting – Protect against DDoS
Testing & Monitoring
Unit Tests – Test services and controllers
Integration Tests – Test API endpoints with mock database
Postman/Newman – Manual and automated testing
Load Testing – JMeter, k6 for performance testing
Logging & Tracing – Serilog, OpenTelemetry
API Monitoring – New Relic, Datadog, Prometheus + Grafana
API Analytics
Track key metrics:
Real-World Use Cases
E-commerce → Product catalog APIs, order APIs
Banking → Payment APIs, transaction APIs
Social Media → Post, comment, like APIs
IoT → Device telemetry APIs
SaaS → Integrations with external CRMs, ERPs
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