What would be the best way to process credit card transactions in an AEM site?

Processing credit card transactions on an AEM site is best accomplished through an external system. This approach leverages specialized payment gateways or third-party services that are designed to handle sensitive financial information securely and in compliance with industry standards, such as PCI DSS (Payment Card Industry Data Security Standard).

Utilizing an external system mitigates risks associated with dealing directly with sensitive credit card information on your site, such as security vulnerabilities that could lead to data breaches or fraud. External systems also tend to offer additional features like fraud detection, transaction logging, and customer support, which enhance the overall transaction experience.

While other options might seem relevant, they don't provide the necessary level of security or functionality needed for managing financial transactions. For instance, JavaScript alone cannot securely handle transactions and risk exposure to vulnerabilities. The shopping cart component does help to facilitate sales processes but typically interfaces with an external payment processor rather than directly handling credit card information. Storing credit card information in the JCR is highly discouraged due to severe security implications and regulatory compliance issues. Thus, relying on an external system ensures that best practices in payment processing are followed.