Exam AWS Certified Solutions Architect - Associate SAA-C03 topic 1 question 81 discussion

decoupled = SQS Launch template = AMI Launch configuration = EC2

This design follows the best practices for loosely coupled and scalable architecture. By using SQS, the jobs are durably stored in the queue, ensuring they are not lost. The processor application is stateless, which aligns with the design requirement. The AMI allows for consistent deployment of the application. The launch template and ASG facilitate the dynamic scaling of the application based on the number of items in the SQS, ensuring parallel processing of jobs. Options A and D suggest using SNS, which is a publish/subscribe messaging service and may not provide the durability required for job storage. Option B suggests using network usage as a scaling metric, which may not be directly related to the number of jobs to be processed. The number of items in the SQS provides a more accurate metric for scaling based on the workload.

Ans C - decoupled and durable (SQS), auto-scaling based on number of messages.

C for sure

SNS is not reliable in case of processing failure which is why none of the SNS options are useful. SQS (not in FIFO mode) allows parallel message processing but reliability/durability of messages is guaranteed. AMI/EC2 scaling is good choice and scaling parameter should be number of messages. Hence "C" is the correct answer

"Based on the number of jobs to be processed" -> that alone rules out ABD because only C is based on queue length. (D is based on "number of messages published to the queue", not number of messages currently in queue.) "Job items are durably stored" also speaks for SQS over SNS.

so many words...

from my perspective, I didn't go for D even though it provides decoupled architecture is because in the question they said "parallel processing" SNS sends the same message to all the subscribers, but in this case we don't want all the nodes to process the same message instead we want them to process as much jobs as possible in a parallel fashion. SQS in this case is more suitable because each job will get a message and process it and the next message will be taken by another job and so on..

https://aws.amazon.com/about-aws/whats-new/2021/03/aws-certificate-manager-provides-certificate-expiry-monitoring-through-amazon-cloudwatch/

Loosely coupled = Amazon SQS queue New application being deployed = deploy on Amazon Machine Image Adding and removing application nodes as needed based on the number of jobs to be processed = Auto Scaling group with launch template

The recommended design is to use an SQS queue to store jobs (option C): SQS provides a durable and decoupled queue to store job items An Auto Scaling group with scaling policies based on SQS queue length will add/remove nodes as needed Launch templates provide flexibility to update AMIs The key points: SQS enables loose coupling and stores jobs durably Auto Scaling provides parallel processing Scaling based on queue length manages nodes effectively

C for sure

***CORRECT*** The correct design is Option C. Create an Amazon SQS queue to hold the jobs that need to be processed. Create an Amazon Machine Image (AMI) that consists of the processor application. Create a launch template that uses the AMI. Create an Auto Scaling group using the launch template. Set the scaling policy for the Auto Scaling group to add and remove nodes based on the number of items in the SQS queue. This design satisfies the requirements of the application by using Amazon Simple Queue Service (SQS) as durable storage for the job items and Amazon Elastic Compute Cloud (EC2) Auto Scaling to add and remove nodes based on the number of items in the queue. The processor application can be run in parallel on multiple nodes, and the use of launch templates allows for flexibility in the configuration of the EC2 instances.

SQS with EC2 autoscaling policy based number of messages in the queue.

C is correct

what about the word "coupled"

AWS strongly recommends that you do not use launch configurations hence answer is C https://docs.amazonaws.cn/en_us/autoscaling/ec2/userguide/launch-configurations.html