Statelessness requirement in Rest API

Introduction

Statelessness means each request from a client to a server must contain all the information needed to understand and process the request. The server does not remember anything from previous requests.

When building web services that need to handle many users at the same time.

When you want your service to be easy to scale by adding more servers.

When you want to make your API simple and reliable without storing user data between requests.

When you want to avoid problems caused by lost or outdated session data.

When you want your service to work well with caching and load balancing.

Syntax

Rest API

HTTP Request:
GET /resource HTTP/1.1
Host: example.com
Authorization: Bearer <token>
Content-Type: application/json

{
  "data": "value"
}

All information needed to process the request is sent in the request itself.

The server does not keep any session or user state between requests.

Examples

The request includes an authorization token so the server can identify the user without storing session data.

Rest API

GET /profile HTTP/1.1
Host: api.example.com
Authorization: Bearer abc123token

The order details and user token are sent together in the request. The server processes it without remembering past orders.

Rest API

POST /order HTTP/1.1
Host: api.example.com
Content-Type: application/json
Authorization: Bearer abc123token

{
  "item": "book",
  "quantity": 1
}

Sample Program

This simple web service greets the user by name. Each request must include the name as a query parameter. The server does not remember any previous requests.

Rest API

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/greet', methods=['GET'])
def greet():
    name = request.args.get('name')
    if not name:
        return jsonify({'error': 'Name is required'}), 400
    return jsonify({'message': f'Hello, {name}!'})

if __name__ == '__main__':
    app.run(debug=True)

Important Notes

Statelessness helps servers handle many requests independently and reliably.

Clients must send all needed data with each request, like authentication tokens or parameters.

Stateless APIs are easier to scale and cache.

Summary

Statelessness means no memory of past requests on the server.

Each request must have all information needed to be understood alone.

This makes APIs simpler, scalable, and reliable.