Describe the data flow when buying a book — the client is authorized, on the book page, wants to buy it. Where does the API Gateway request go?

When an authorized client on the book page clicks the "Buy" button, the following data flow occurs:

1. The client sends a purchase request through the API Gateway.
2. The API Gateway authenticates the request and forwards it to the order management service.
3. The order service checks the availability of the book, the user's status, and creates an order.
4. The request is then sent to the payment service to process the transaction.
5. After successful payment, the payment service notifies the order service of the confirmation.
6. The order service updates the order status and initiates sending a notification to the client.
7. The client receives the purchase confirmation.

Thus, the API Gateway acts as the entry point and routes the request to the order service, which coordinates further actions with other system services.