SAA-C03 Question 520
Single answerA company is running a multi-tier application in AWS. The front-end web servers are hosted in an Auto Scaling group behind an Application Load Balancer (ALB). The application servers and database servers are hosted in private subnets. The company wants to minimize data transfer costs while ensuring secure communication between the tiers. Which design change should you implement?
- A
Enable VPC peering between the subnets hosting the application servers and database servers.
- B
Replace the Application Load Balancer with a Network Load Balancer to reduce data transfer costs.
- C
Configure the Auto Scaling group and ALB to use the same Availability Zone wherever possible.
- D
Ensure all communication between the tiers happens within the same VPC and over private IPs.
Show answer and explanation
Correct answer: D
Explanation
In this scenario, the most cost-optimized and secure network design involves ensuring that all communication between application components (web servers, application servers, and database servers) takes place within the same VPC over private IPs. This avoids inter-VPC or public internet data transfer costs and ensures secure communication by keeping the traffic within the AWS network.
- A. Incorrect.
VPC peering is unnecessary here because all components are already in the same VPC. VPC peering is used to connect different VPCs, not subnets within the same VPC, so it does not apply to this scenario.
- B. Incorrect.
Replacing the ALB with a Network Load Balancer will not optimize costs since both ALBs and NLBs incur similar charges for inter-AZ data transfer and this solution does not address the need for secure communication.
- C. Incorrect.
Configuring the Auto Scaling group and ALB to use the same Availability Zone may slightly reduce costs but sacrifices high availability, which is a key AWS design principle.
- D. Correct.
Ensuring all communication between the tiers happens within the same VPC and over private IPs effectively minimizes data transfer costs by avoiding inter-AZ data transfer charges and ensures secure communication.