Exam AWS Certified Solutions Architect - Associate SAA-C03 topic 1 question 75 discussion

Agree with A>>> Lambda = serverless + autoscale (modernize), SQS= decouple (no more drops)

The catch phrase is "scale up when communication failures are detected" Scaling should not be based on communication failures, that'll be crying over spilled milk ! or rather too late. So D is wrong.

why its not c?

Ans A - keep it simple: API Gateway + Lambda + SQS D won't work: it relies upon a failure detected - by then its too late)

The answer choice D cannot be the answer because CloudWatch is not an appropriate way to monitor transaction failures. I would have been more confused about it if CloudWatch hadn't been mentioned.

RESTful services = API Gateways https://docs.aws.amazon.com/apigateway/latest/developerguide/welcome.html

Least operational overhead = API Gateway + Lambda + SQS BC wrong applications D: Will work but more operational overhead than A with less resilience to failures

You want to "modernize the application", that a modern application is serverless, in any case a modern application does NOT use EC2 instances. Also, managing EC2 instances (with the OS etc pp) is NOT "operationally efficient". Thus not D.

For me the solution could be based on using SNS with multiple topics to organize communication between different tiers ( Using Subscriber for one and Producer for another topic to proceed with transactions over multi-tiers ). CloudWatch to monitor SNS topics queue length and scale up/down based on counts of messages (NumberOfMessagesPublished)

A is the perfect answer no need for the ASG

D is better because in answer A there is a bottleneck on a SQS - service app, D is as operationally efficient as A and solves the above issue

ASG is not as efficient as Lambda!

I feel the answer is D, Lambda would increase the complexity and overhead and it has limitation of running for 15 min.

MOST operationally efficient = Serverless = AWS Lambda functions, Amazon Simple Queue Service

A and D are both good solution however A will suffice the requirement as it is the most operational efficient for modern applications, AWS Lambda will scale elastically when application will become overloaded and the fact that it is serverless. SQS will handle the queue as well..

This solution addresses the issue of dropped transactions by decoupling the communication between application tiers using SQS. It ensures that transactions are not lost even if one tier becomes overloaded. By using EC2 in ASG, the application can automatically scale based on the demand and the length of the SQS. This allows for efficient utilization of resources and ensures that the application can handle increased workload and communication failures. CloudWatch is used to monitor the length of SQS. When queue length exceeds a certain threshold, indicating potential communication failures, the ASG can be configured to scale up by adding more instances to handle the load. D. This solution utilizes Lambda and API Gateway, which can be a valid approach for building serverless applications. However, it may introduce additional complexity and operational overhead compared to the requirement of modernizing an existing multi-tiered application.

ANS: A Key word - RESTful services - Amazon API Gateway