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APIs (Application Programming Interfaces) are a critical part of modern software development, and understanding them is essential for technical interviews. Below is a structured roadmap covering everything from basics to advanced concepts, along with practical commands and steps to help you practice.
You Should Know:
Types of APIs
- REST: Most widely used, follows stateless architecture.
- SOAP: XML-based, used in enterprise applications.
- GraphQL: Fetches only required data, flexible queries.
- gRPC: High performance, uses protocol buffers.
- WebSocket APIs: Real-time data transfer.
- OpenAPI (Swagger): Standard for API documentation.
API Methods
- GET: Retrieve data.
- POST: Create a new resource.
- PUT: Update an existing resource.
- DELETE: Remove a resource.
- PATCH: Partially update a resource.
- HEAD: Get headers without the response body.
- OPTIONS: Check supported HTTP methods.
Authentication and Security
- JWT (JSON Web Tokens): Stateless authentication.
- API Keys: Simple authentication method.
- OAuth 2.0: Secure authorization for third-party access.
- OpenID Connect: Extends OAuth with identity verification.
- HMAC (Hash-Based Message Authentication Code): Secure message authentication.
- SSL/TLS Encryption: Secure data transmission.
- Rate Limiting & Throttling: Prevent abuse and DoS attacks.
- Input Validation: Protect against injection attacks.
- CSRF Protection: Prevent cross-site request forgery.
- Access Control (Roles & Permissions): Restrict access based on user roles.
- IP Whitelisting: Allow requests only from trusted sources.
API Design Principles
- Statelessness: Each request is independent.
- Versioning: Manage API changes efficiently.
- Pagination: Load large datasets efficiently.
- Caching: Reduce load and improve response time.
- Idempotency: Ensure repeatable requests produce the same result.
- Error Handling: Provide clear and meaningful error responses.
API Testing
- Unit Testing: Test individual components.
- Integration Testing: Verify API interactions.
- Security Testing: Identify vulnerabilities.
- Performance Testing: Measure API speed and load handling.
- Load Testing: Test API under heavy traffic.
API Documentation
- OpenAPI (Swagger): Standardized API documentation.
- API Blueprint: Human-readable API design format.
- Postman Collections: Organize and test API requests.
API Versioning
- URI Versioning: `/v1/users` vs.
/v2/users. - Header Versioning: Use custom headers for versions.
- Query Parameter Versioning: Example:
?version=1. - Content Negotiation: Different versions based on request headers.
Tools and Frameworks
- Postman: API testing and automation.
- Swagger (OpenAPI): API documentation and design.
- Insomnia: Lightweight API testing tool.
- Apigee: API management platform.
- AWS API Gateway: Manage and deploy APIs.
- Express.js: Build RESTful APIs with Node.js.
- RAML: Define RESTful APIs with a structured approach.
Practice Verified Codes and Commands
1. Testing APIs with cURL
<h1>GET request</h1>
curl -X GET https://api.example.com/users
<h1>POST request with JSON data</h1>
curl -X POST https://api.example.com/users -H "Content-Type: application/json" -d '{"name": "John", "age": 30}'
<h1>PUT request</h1>
curl -X PUT https://api.example.com/users/1 -H "Content-Type: application/json" -d '{"name": "John Doe"}'
<h1>DELETE request</h1>
curl -X DELETE https://api.example.com/users/1
2. Using Postman for API Testing
- Install Postman from Postman’s Official Website.
- Create a new collection and add requests for GET, POST, PUT, and DELETE.
- Use environment variables to manage different API endpoints.
3. Generating JWT Tokens
<h1>Install jwt-cli for generating tokens</h1>
npm install -g jwt-cli
<h1>Generate a JWT token</h1>
jwt encode --secret "your-secret-key" '{"user_id": 123, "role": "admin"}'
4. Setting Up SSL/TLS with OpenSSL
<h1>Generate a private key</h1> openssl genpkey -algorithm RSA -out private-key.pem <h1>Generate a certificate signing request (CSR)</h1> openssl req -new -key private-key.pem -out csr.pem <h1>Generate a self-signed certificate</h1> openssl x509 -req -days 365 -in csr.pem -signkey private-key.pem -out certificate.pem
5. Load Testing with Apache Bench (ab)
<h1>Install Apache Bench</h1> sudo apt-get install apache2-utils <h1>Run a load test</h1> ab -n 1000 -c 100 https://api.example.com/users
What Undercode Say
APIs are the backbone of modern applications, and mastering them is crucial for any developer. Practice the commands and tools mentioned above to gain hands-on experience. Use Postman for API testing, cURL for quick requests, and OpenSSL for securing your APIs. Don’t forget to explore advanced topics like JWT, OAuth 2.0, and API versioning to ace your interviews. For further reading, check out the OpenAPI Specification and Postman Documentation.
Useful URLs:
References:
Reported By: Akashsinnghh Struggling – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
