AWS Certified Solutions Architect – Associate (SAA-C03) — Question 948
A company operates a food delivery service. Because of recent growth, the company's order processing system is experiencing scaling problems during peak traffic hours. The current architecture includes Amazon EC2 instances in an Auto Scaling group that collect orders from an application. A second group of EC2 instances in an Auto Scaling group fulfills the orders.
The order collection process occurs quickly, but the order fulfillment process can take longer. Data must not be lost because of a scaling event.
A solutions architect must ensure that the order collection process and the order fulfillment process can both scale adequately during peak traffic hours.
Which solution will meet these requirements?
Answer options
- A. Use Amazon CloudWatch to monitor the CPUUtilization metric for each instance in both Auto Scaling groups. Configure each Auto Scaling group's minimum capacity to meet its peak workload value.
- B. Use Amazon CloudWatch to monitor the CPUUtilization metric for each instance in both Auto Scaling groups. Configure a CloudWatch alarm to invoke an Amazon Simple Notification Service (Amazon SNS) topic to create additional Auto Scaling groups on demand.
- C. Provision two Amazon Simple Queue Service (Amazon SQS) queues. Use one SQS queue for order collection. Use the second SQS queue for order fulfillment. Configure the EC2 instances to poll their respective queues. Scale the Auto Scaling groups based on notifications that the queues send.
- D. Provision two Amazon Simple Queue Service (Amazon SQS) queues. Use one SQS queue for order collection. Use the second SQS queue for order fulfillment. Configure the EC2 instances to poll their respective queues. Scale the Auto Scaling groups based on the number of messages in each queue.
Correct answer: D
Explanation
Using Amazon SQS queues decouples the order collection and fulfillment processes, ensuring that messages (orders) are not lost during scaling events. Scaling the Auto Scaling groups based on the number of messages in the queues (queue depth) allows the EC2 instances to scale dynamically in response to the actual backlog of work. Scaling based on queue notifications is incorrect because SQS does not natively send scaling notifications to Auto Scaling groups, making option D the correct choice.