An e-commerce site that wants to keep a purchase record for each of its customers. What technology should be used to achieve that?

To keep a purchase record for each customer on an e-commerce site, the following technologies can be considered:

1. Database Management System (DBMS): Use a relational database like MySQL, PostgreSQL, or a NoSQL database like MongoDB to store customer and purchase records. This allows for efficient data retrieval, manipulation, and storage.

2. Backend Framework: A backend framework like Node.js, Django, or Ruby on Rails can be used to handle server-side logic, manage database connections, and process purchase transactions.

3. API (Application Programming Interface): Implement RESTful APIs to facilitate communication between the frontend and backend, allowing the e-commerce site to send and receive customer purchase data.

4. Cloud Storage Solutions: For additional scalability and data backup, cloud services like AWS, Google Cloud, or Azure can be utilized to store purchase records securely.

5. Payment Gateway Integration: Integrate a payment gateway like Stripe or PayPal to process transactions and securely record payment information associated with each purchase.

6. Authentication and Authorization: Implement secure authentication and authorization mechanisms to ensure that customer data is protected and only accessible to authorized users.

These technologies collectively ensure an efficient, secure, and reliable system for keeping records of customer purchases on an e-commerce site.