Efficient and Secure Instance Updates in a Private Subnet

As an architect, the most efficient and secure solution for instances hosted in a private subnet in a VPC to download updates from the Internet would be to use a NAT Gateway.

A NAT Gateway is a highly available AWS-managed service that allows instances in a private subnet to connect to the Internet, but does not allow the Internet to initiate connections back to the instances. With a NAT Gateway, the instances can access software updates and patches without being exposed to the public Internet.

Option A, creating a new public subnet and moving the instance to that subnet, is not a secure solution because it exposes the instance to the public Internet, which can increase the risk of security breaches. Additionally, it requires additional management and monitoring to maintain the security of the instance.

Option B, creating a new EC2 instance to download updates separately and then pushing them to the required instance, is not an efficient solution because it requires additional resources and management to maintain the update process. This option also increases the attack surface of the environment, as the new EC2 instance would also need to be secured and monitored.

Option D, creating a VPC link to the Internet, is not as secure as using a NAT Gateway because it requires a direct route between the private subnet and the Internet. This option can also be less efficient, as it may require additional configuration and management to ensure the security of the VPC link.

Therefore, using a NAT Gateway is the most efficient and secure option for instances hosted in a private subnet in a VPC to download updates from the Internet.