A rental payment startup has developed a web portal that enables users to pay for their rent using both their credit and debit cards online. They are using a third-party payment service to handle and process credit card payments on their platform since the portal is not fully compliant with the Payment Card Industry Data Security Standard (PCI DSS). The application is hosted in an Auto Scaling group of Amazon EC2 instances, which are launched in private subnets behind an internal-facing Application Load Balancer. The system must connect to an external payment service over the Internet to complete the transaction for every user payment. As a DevOps Engineer, what would be the MOST suitable option to implement to satisfy the above requirement?