Answer: VPC endpoint

## Explanation **VPC endpoints** (specifically VPC endpoints for S3) are the correct solution for this requirement because: 1. **Traffic stays within AWS network**: VPC endpoints for S3 allow EC2 instances in a VPC to access S3 without traversing the public internet. The traffic remains within the AWS network infrastructure. 2. **Security compliance**: This meets the CISO's requirement that "no application traffic between the two services should traverse the public internet." 3. **Direct connectivity**: VPC endpoints provide a direct, private connection between your VPC and AWS services like S3. **Why the other options are incorrect:** - **A. AWS Key Management Service (AWS KMS)**: This is for encryption key management, not for network routing. While S3 encryption might use KMS, this doesn't address the network traffic requirement. - **C. Private subnet**: Private subnets prevent internet access for EC2 instances, but traffic from a private subnet to S3 would still go through the internet gateway and traverse the public internet unless a VPC endpoint is used. - **D. Virtual private gateway**: This is for connecting your VPC to on-premises networks via VPN or Direct Connect, not for accessing AWS services privately. **Additional context:** - There are two types of VPC endpoints: **Interface endpoints** (powered by AWS PrivateLink) for most AWS services, and **Gateway endpoints** specifically for S3 and DynamoDB. - For S3, you would use a **Gateway endpoint** which doesn't require ENIs and is free to use. - This solution ensures that data transfer between EC2 and S3 remains secure and compliant with the organization's security policies.

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