REST — resources, verbs, statelessness, HATEOAS, versioning, idempotency. The most common API style and its tradeoffs.

What is REST?

REST (Representational State Transfer) is an architectural style for designing networked applications. RESTful APIs use HTTP methods to perform CRUD operations on resources.

REST Principles

Principle	Description
Stateless	Each request contains all info needed
Client-Server	Separation of concerns
Cacheable	Responses can be cached
Uniform Interface	Consistent resource-based URLs
Layered System	Client doesn't know if talking to server or intermediary

Resource-Based URLs

Good (resource-based):
GET    /users           # List users
GET    /users/123       # Get user 123
POST   /users           # Create user
PUT    /users/123       # Update user 123
DELETE /users/123       # Delete user 123

Bad (action-based):
GET /getUser?id=123
POST /createUser
POST /deleteUser

HTTP Methods in REST

Operation	Method	Example
Create	POST	`POST /users`
Read	GET	`GET /users/123`
Update (full)	PUT	`PUT /users/123`
Update (partial)	PATCH	`PATCH /users/123`
Delete	DELETE	`DELETE /users/123`

Request/Response Example

Request

POST /api/users HTTP/1.1
Host: api.example.com
Content-Type: application/json

{
  "name": "John",
  "email": "john@example.com"
}

Response

HTTP/1.1 201 Created
Content-Type: application/json
Location: /api/users/123

{
  "id": 123,
  "name": "John",
  "email": "john@example.com"
}

Best Practices

Practice	Example
Use nouns, not verbs	`/users` not `/getUsers`
Use plural nouns	`/users` not `/user`
Nest for relationships	`/users/123/orders`
Use query params for filtering	`/users?role=admin`
Version your API	`/v1/users` or header

Pagination

GET /users?page=2&limit=20

Response:
{
  "data": [...],
  "pagination": {
    "page": 2,
    "limit": 20,
    "total": 100,
    "next": "/users?page=3&limit=20"
  }
}

Interview Tips

Explain REST principles (stateless, uniform interface)
Design resource-based URLs properly
Know when to use each HTTP method
Discuss pagination, filtering, versioning
Compare with GraphQL and gRPC

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REST

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