A company is running an application in the AWS Cloud. The application consists of microservices that run on a fleet of Amazon EC2 instances in multiple Availability Zones behind an Application Load Balancer. The company recently added a new REST API that was implemented in Amazon API Gateway. Some of the older microservices that run on EC2 instances need to call this new API. The company does not want the API to be accessible from the public internet and does not want proprietary data to traverse the public internet. What should a solutions architect do to meet these requirements?