An application is hosted in an AWS EC2 instance in a VPC private subnet. The application frequently downloads a large amount of files stored in an S3 bucket. A NAT Gateway is configured in the public subnet for the EC2 instance to connect with the S3 bucket. Now you need to take some actions to reduce the cost of AWS infrastructure. Which method is the most appropriate?

Answer options:

A.Replace the NAT Gateway with a t2.micro NAT instance.
B.Configure a gateway endpoint for Amazon S3. Delete the NAT Gateway.
C.Place the EC2 instance in the public subnet. Delete the NAT Gateway.
D.Replace the NAT Gateway with an Internet Gateway. Configure an AWS PrivateLink for Amazon S3.

Correct Answer – B
Option A is incorrect: Because the NAT instance is not recommended because of its performance issue. In this scenario, NAT Gateway can be deleted if the VPC gateway endpoint is configured for S3.
Option B is CORRECT: Because with this method, you do not need to pay for the NAT Gateway or the internet data transfer for S3. Besides, the VPC gateway endpoint is a free service.
Option C is incorrect: Because you still need to pay for the internet data transfer for S3. It may also cause security issues as the EC2 instance is put in the public subnet.
Option D is incorrect: Because the Internet Gateway cannot replace the NAT Gateway.
Reference:
https://docs.aws.amazon.com/vpc/latest/userguide/vpce-gateway.html#gateway-endpoint-pricing