REST API Design

REST API design is about exposing resources through predictable URLs and HTTP methods.

Resource-based URLs

Use nouns, not actions.

Good:

GET /users
POST /users
GET /users/:id
PATCH /users/:id
DELETE /users/:id

Avoid:

POST /createUser
POST /deleteUser
GET /getAllUsers

HTTP method already describes the action.

Status codes

Common status codes:

Example response shape

Success:

{
  "data": {
    "id": "123",
    "name": "Asha"
  }
}

Error:

{
  "error": {
    "message": "User not found"
  }
}

Common mistake

Do not return 200 OK for every response.

If validation fails, use 400.

If user is not logged in, use 401.

If resource does not exist, use 404.

Interview answer

REST APIs model data as resources and use HTTP methods to perform actions on them. URLs should be noun-based, methods should express actions, status codes should describe results, and responses should follow a consistent shape.