A client wants to buy a book — where does the request go and in what form?

When a client wants to buy a book, the request usually comes in the form of an HTTP request to the online store's server or API.

For example, the client clicks the "Buy" button on the website, and the browser sends a POST request to an endpoint, such as /purchase or /orders.

The request body typically includes data:

• Book identifier (e.g., book_id)
• Quantity
• User data (ID, delivery address, etc.)
• Payment information or payment token

Example JSON request:

{
  "book_id": "12345",
  "quantity": 1,
  "user_id": "67890",
  "payment_token": "tok_abc123"
}

This request is received by the backend service, which processes the order: checks the availability of the book, reserves the item, initiates the payment, and creates an order record in the database.