Which solution will meet these requirements?
Replace the NAT gateways with NAT instances. In the VPC route table, create a route from the private subnets to the NAT instances.
Move the EC2 instances to the public subnets. Remove the NAT gateways.
Set up an S3 gateway VPC endpoint in the VPC. Attach an endpoint policy to the endpoint to allow the required actions on the S3 bucket.
Attach an Amazon Elastic File System (Amazon EFS) volume to the EC2 instances. Host the image on the EFS volume.
Explanations:
Replacing NAT gateways with NAT instances may reduce costs but introduces more operational overhead for managing and scaling NAT instances. This approach compromises the high availability and fault tolerance of the solution.
Moving EC2 instances to the public subnets would expose them directly to the internet, violating the security requirement of keeping the service highly secure. Additionally, it eliminates the use of private subnets, which are best practices for security.
Setting up an S3 gateway VPC endpoint eliminates the need for NAT gateways while maintaining secure communication between the EC2 instances and S3. This reduces costs and operational complexity while preserving security by keeping traffic within the AWS network.
Amazon Elastic File System (EFS) is not necessary for this scenario because the service uses Amazon S3 for image storage, and the solution involves reducing costs. EFS is designed for shared file systems, not for storing large amounts of data for image processing as S3 is better suited.
I assess that the answer is:
Set up an S3 gateway VPC endpoint in the VPC. Attach an endpoint policy to the endpoint to allow the required actions on the S3 bucket.