Which solution will meet these requirements?
Create an S3 gateway endpoint that uses the default gateway endpoint policy. Associate the private subnet with the gateway endpoint.
Create an S3 interface endpoint. Associate the EC2 instances with the interface endpoint.
Configure a NAT gateway. Associate the private subnet with the NAT gateway.
Configure a proxy EC2 instance. Update the private subnet route tables to route traffic through the proxy EC2 instance. Configure the proxy to route all S3 requests to the target S3 bucket.
Explanations:
An S3 gateway endpoint allows EC2 instances in a private subnet to access S3 buckets directly without needing an internet connection. The default endpoint policy allows full access to S3, meeting the requirement for the EC2 instances to access S3 without changes to the instances or application.
An S3 interface endpoint is used for VPC endpoints for S3 that require an interface rather than a gateway, but in this scenario, a gateway endpoint is sufficient and simpler. It does not provide the same functionality as a gateway endpoint for the specific use case of accessing S3 from a private subnet.
A NAT gateway provides internet access to private subnets, which is not suitable as the requirement specifies that the EC2 instances must not have access to the internet. NAT would allow outbound internet access, violating the requirement.
Configuring a proxy EC2 instance adds unnecessary complexity and management overhead. It requires changes to the private subnet’s route tables and involves additional configuration, which contradicts the requirement of not making changes to the EC2 instances or application.
I rank that the answer is:
Create an S3 gateway endpoint that uses the default gateway endpoint policy. Associate the private subnet with the gateway endpoint.