Exam AWS Certified Solutions Architect - Professional SAP-C02 topic 1 question 179 discussion

I would go with B just because of the wording. I believe A should work just fine, but the question asks for "scale in and out based on the number of events." In my opinion, that is what SNS->Lambda->SQS(DLQ) would do, too; I think the SNS->Lambda scale in/out behavior is more implicit. So I will go with B here because it is more explicit.

Configuring scaling based on the age of the oldest message is nowhere near as good as scaling based on size of the Queue for this use case. age of the oldest message will grow linearly based on time. If there is a dramatic spike in the Queue size due to increased traffic, like 100X increase in size. Then the queue will have grown a lot but the oldest message will only increase in age linearly, so the scaling will not be able to realize how much the workload has increased.

People who are choosing A. Have you done associate level certs as this does not make any sense. You shouldnt be attempting this exam if that's how lost you are.

The Auto Scaling group of EC2 instances can automatically adjust the number of instances based on the ApproximateAgeOfOldestMessage metric. This ensures that the solution scales dynamically with the volume of events, maintaining efficient processing. https://docs.aws.amazon.com/autoscaling/ec2/userguide/as-using-sqs-queue.html

B for sure

I do think the B is correct way with ApproximateNumberOfMessages instead of ApproximateAgeOfOldestMessage. there is no such metric ...AgeOfOldestMessage

publishing events to an SQS queue, creating an EC2 Auto Scaling group that scales based on the queue's ApproximateAgeOfOldestMessage metric, and configuring the application to write failed messages to a dead-letter queue provides a scalable, fault-tolerant, and cost-effective solution for event processing with the ability to handle processing errors separately.

Vote for A

A seems better. Dont really know.

Option B. Question states, " must move to into a separate queue for review" Dead-Letter queues give you this capability for debugging or troubleshooting the issue. https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-dead-letter-queues.html

A fulfils all objectives. In B, ApproximateAgeOfOldestMessage doesn't translate to a reliable scaling pattern, and EC2s are implied. C does not implement a dead-letter queue D is overengineered.

SQS with DLQ

ApproximateAgeOfOldestMessage metric may not be as responsive as needed, and it doesn't directly address the requirement for handling processing errors by moving events to a separate queue for review.

The question typical AWS thrown words and leaving gaps.. but still going for B

I would go with A. Scaling in/out based on message age does not align with what question asks i.e. it should be based on the number of events. So, B is not right here.

Answer is B I would go with A, except a Dead Letter Q is not an SQS queue. There are only two types of SQS Queues, namely, Standard and FIFO. A DLQ is a special message queue (not SQS). See here for confirmation: https://aws.amazon.com/what-is/dead-letter-queue/#:~:text=A%20dead%2Dletter%20queue%20(DLQ)%20is%20a%20special%20type,communication%20in%20a%20distributed%20system.

I prefer A as the solution is serverless.