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HTTP Methods

Master GET, POST, PUT, PATCH, DELETE and their semantics.

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HTTP Methods Overview

HTTP methods define the action to be performed on a resource. Each method has specific semantics:

CRUD Operations Mapping:
┌──────────┬─────────────┬───────────┬──────────┐
│ Operation│ HTTP Method │ Idempotent│ Safe     │
├──────────┼─────────────┼───────────┼──────────┤
│ Create   │ POST        │ No        │ No       │
│ Read     │ GET         │ Yes       │ Yes      │
│ Update   │ PUT         │ Yes       │ No       │
│ Update   │ PATCH       │ No        │ No       │
│ Delete   │ DELETE      │ Yes       │ No       │
└──────────┴─────────────┴───────────┴──────────┘

Safety and Idempotency

Safe — Doesn't modify the server state (GET, HEAD, OPTIONS)
Idempotent — Same request produces same result (GET, PUT, DELETE)

GET /users/123      → Safe (read only)
POST /users         → Not safe, not idempotent
PUT /users/123      → Not safe, but idempotent
DELETE /users/123   → Not safe, but idempotent
PATCH /users/123    → Not safe, not idempotent

Method Comparison

Method Body Cacheable Idempotent Safe
GET No Yes Yes Yes
HEAD No Yes Yes Yes
POST Yes Conditional No No
PUT Yes No Yes No
PATCH Yes No No No
DELETE Yes No Yes No
OPTIONS No No Yes Yes

RESTful API Design

GET    /api/products          → List all products
GET    /api/products/123      → Get product 123
POST   /api/products          → Create new product
PUT    /api/products/123      → Replace product 123
PATCH  /api/products/123      → Update fields of product 123
DELETE /api/products/123      → Delete product 123

Why Method Semantics Matter

Using the wrong method causes problems:

  • Using GET for mutations — Browsers prefetch/crawl GET URLs
  • Using POST for idempotent ops — Retries create duplicates
  • Using PUT instead of PATCH — Must send full resource every time

Implementation Details

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 HTTP Methods is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Practice Problems

0/3solved
Implement HTTP Methods

Design and implement a solution for HTTP Methods in a backend system. Consider scalability, error handling, and production readiness.

Solution
// HTTP Methods implementation
// Key aspects: validation, error handling, logging, testing

public class HTTPMethods {
    // Production-ready implementation
}
HTTP Methods Edge Cases

Identify and handle edge cases for HTTP Methods. 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, idempotency
HTTP Methods Testing Strategy

Write a testing strategy for HTTP Methods. Include unit tests, integration tests, and performance tests.

Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injection

Quiz

1. Which HTTP methods are considered safe (don't modify server state)?

Question 1 options

2. Why is PUT idempotent but POST is not?

Question 2 options

3. What is the primary purpose of HTTP Methods?

Question 3 options

4. What is a common mistake when implementing HTTP Methods?

Question 4 options

Flashcards

Question

What are the 5 main HTTP methods?

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Answer

GET, POST, PUT, PATCH, DELETE

Question

What does idempotent mean?

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Answer

Same request produces same result — GET, PUT, DELETE are idempotent

Question

What is HTTP Methods?

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Answer

HTTP Methods is a key concept in backend development.

Question

When to use HTTP Methods?

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Answer

Use HTTP Methods when building production systems that require reliability, scalability, and maintainability.

Question

HTTP Methods best practices

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Answer

Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.

Revision Notes

Key Takeaways

  • 1.HTTP methods define the action on a resource
  • 2.Safe: GET, HEAD, OPTIONS (no server mutation)
  • 3.Idempotent: GET, PUT, DELETE (same result on retry)
  • 4.REST maps CRUD to GET, POST, PUT/PATCH, DELETE

Interview Tips

  • •Explain why idempotency matters for retries
  • •Know when to use PUT vs PATCH

Cheat Sheet

HTTP Methods

  • GET: Read (safe, idempotent)
  • POST: Create (not safe, not idempotent)
  • PUT: Replace (idempotent)
  • PATCH: Partial update (not idempotent)
  • DELETE: Remove (idempotent)