Book Purchase Service with Multi-Store Price Aggregation

databricks Design a web service system for customers to purchase books. The customer provides book information, credit card details, and the maximum price they are willing to pay. The system needs to connect to multiple bookstore APIs to find the lowest price. If the lowest price is below the customer's maximum acceptable price, the transaction is completed and paid; otherwise, the lowest price is returned to the customer. The service must handle 50 to 200 bookstores and 1 to 2 million books. Latency should be within 10-20 seconds. Example Input 12345 150 100