A company is managing a customer`s application which currently includes a three-tier application configuration. The first tier manages the web instances and is configured in a public subnet in an AWS VPC. The second layer is the application layer. As part of the application code, the application instances upload large amounts of data to Amazon S3. Currently, the private subnets that the application instances are running on have a route to a single t2.micro NAT instance. The application, during peak loads, becomes slow, and customer uploads from the application to S3 are not completing and taking a long time. Which steps might you take to solve the issue using the most cost-efficient method? Choose the correct answer from the options below.

Answer options:

A.Configure Auto Scaling for the NAT instance to handle an increase in load.
B.Create a VPC S3 endpoint.
C.Increase the NAT instance size; network throughput increases with an increase in instance size.
D.Launch an additional NAT instance in another subnet and replace one of the routes in a subnet with the new instance.

Answer – B
In this scenario, the NAT instance is the bottleneck which during the peak loads becomes slow. The possible solutions are either to scale up or scale out the NAT instance or setup S3 as the endpoint of the VPC. So that the VPC can privately and securely connect to the S3 buckets. See the images below for setting up the S3 as VPC Endpoint.
Option A is incorrect because even though placing NAT instances in auto-scale would handle the increase in load, the addition of the NAT instances would not be as cost-efficient as creating an S3 endpoint.
Option B is CORRECT because, with the S3 Endpoint, the VPC can privately and securely connect to the S3 buckets. No additional infrastructure provisioning such as NAT or Gateway is needed, hence saving the cost.
Option C is incorrect because increasing in NAT instance size would add to the cost.
Option D is incorrect because provisioning additional NAT instances would add to the cost.
For more information on VPC endpoints, please refer to the below URLs-
https://aws.amazon.com/blogs/aws/new-vpc-endpoint-for-amazon-s3/
https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-endpoints.html