The GET Method
GET retrieves a representation of a resource. It's the most common HTTP method and the foundation of how the web works.
GET Characteristics
GET /api/users/123 HTTP/1.1
Host: api.example.com
Accept: application/json
→ Safe: Does not modify server state
→ Idempotent: Same request = same response
→ Cacheable: Responses can be cached
→ No request body (server ignores it)
GET Examples
# Get a single resource
GET /api/users/123
# Get a collection with filters
GET /api/users?status=active&role=admin
# Get with pagination
GET /api/products?page=2&limit=20
# Get with field selection
GET /api/users/123?fields=name,email
Response Handling
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: max-age=300
ETag: "abc123"
{
"id": 123,
"name": "Alice",
"email": "alice@example.com",
"role": "admin",
"createdAt": "2026-01-15T10:30:00Z"
}
GET Design Best Practices
- Never use GET for mutations — Browsers prefetch, crawlers follow links
- Use query parameters for filtering — Not path segments for filter values
- Implement pagination — Limit response size
- Support caching — Use ETag, Cache-Control headers
- Return appropriate status codes — 200 for success, 404 for not found
HTTP Best Practices
Methods
- GET: Read (safe, idempotent)
- POST: Create
- PUT: Replace (idempotent)
- PATCH: Partial update
- DELETE: Remove (idempotent)
Headers
- Content-Type: Body format
- Cache-Control: Caching rules
- Authorization: Authentication
- Accept: Desired response format
Status Codes
- 2xx: Success
- 3xx: Redirection
- 4xx: Client error
- 5xx: Server error
Key Points
- Understanding GET is essential for production systems
- Always consider scalability and maintainability
- Test thoroughly before deploying to production
- Monitor performance and set up alerting
Common Patterns
- Validation: Always validate input at the boundary
- Error Handling: Use structured error responses
- Logging: Log key events for debugging
- Testing: Unit, integration, and load tests
- Documentation: Keep docs updated with code changes
Practice Problems
Design and implement a solution for GET in a backend system. Consider scalability, error handling, and production readiness.
Solution
// GET implementation
// Key aspects: validation, error handling, logging, testing
public class GET {
// Production-ready implementation
}Identify and handle edge cases for GET. What happens under high load, with invalid input, or during failures?
Solution
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotencyWrite a testing strategy for GET. Include unit tests, integration tests, and performance tests.
Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injectionQuiz
1. Why should GET never be used for mutations?
2. What is an ETag used for?
3. What is a common mistake when implementing GET?
Flashcards
Question
What does GET do?
Click to reveal answer
Answer
Retrieves a resource — safe, idempotent, cacheable
Question
Why not use GET for mutations?
Click to reveal answer
Answer
Browsers prefetch/crawl GET URLs, causing unintended side effects
Question
GET best practices
Click to reveal answer
Answer
Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.
Revision Notes
Key Takeaways
- 1. GET retrieves resources without modifying server state
- 2. GET is safe, idempotent, and cacheable
- 3. Never use GET for mutations (create, update, delete)
- 4. Use query parameters for filtering, not path segments
Interview Tips
- • Explain why GET must be safe
- • Know how to design pagination for GET endpoints
Cheat Sheet
GET
- Purpose: Read/retrieve resources
- Properties: Safe, Idempotent, Cacheable
- Params: Query string for filters
- Never: Use for mutations (crawlers/prefetch will trigger)