A company hosts ML infrastructure in AWS and the team in the office connects via an IPsec VPN to a VPC. The VPC has enableDnsHostnames and enableDnsSupport set to true, and the office DNS resolvers point to the VPC DNS. The company forbids accessing SageMaker notebooks over the public internet; all access must remain private over the VPN and inside the AWS network. Which solution meets these requirements with the least development effort?

Creating a VPC interface endpoint (AWS PrivateLink) for SageMaker notebooks is the most secure and least effort solution. This allows private connectivity from your VPC to SageMaker API endpoints, including notebooks, without traversing the public internet. Since your office connects via VPN to the VPC, you can directly access the SageMaker notebook through this private endpoint. An EC2 bastion host in a public subnet exposes an EC2 instance to the internet, which is less secure and against the requirement of no public internet access for SageMaker. An EC2 bastion host in a private subnet with a NAT gateway still involves additional EC2 management overhead and doesn't provide direct private access to SageMaker services in the same way PrivateLink does. A NAT gateway allows instances in a private subnet to connect to the internet or other AWS services, but it doesn't create a private connection to SageMaker notebooks from your on-premises network; it would still route traffic over the public internet to SageMaker's public endpoint, which is forbidden.