Your firm has uploaded a large amount of aerial image data to S3. In the past, in your onpremises environment, you used a dedicated group of servers to batch process this data and
used RabbitMQ, an open source messaging system, to get job information to the servers. Once
processed the data would go to tape and be shipped offsite. Your manager told you to stay with
the current design, and leverage AWS archival storage and messaging services to minimize cost.
Which is correct?

A.
Use SNS to pass job messages, use CloudWatch alarms to terminate spot worker instances
when they become idle.
Once data is processed, change the storage class of the S3 object to Glacier.

B.
Use SQS for passing job messages, use CloudWatch alarms to terminate EC2 worker instances
when they become idle.
Once data is processed, change the storage class of the S3 objects to Reduced Redundancy
Storage.

C.
Setup Auto-Scaled workers triggered by queue depth that use spot instances to process
messages in SQS.
Once data is processed, change the storage class of the S3 objects to Reduced Redundancy
Storage.

D.
Setup Auto-Scaled workers triggered by queue depth that use spot instances to process
messages in SQS.
Once data is processed, change the storage class of the S3 objects to Glacier.

Explanation:
The question key part to focus on is “and leverage AWS archival storage and messaging services
to minimize cost.”
For that the storage that is the lowest cost in the answers is Glacier, in addition, the messaging
cost is less for SQS then for SNS if they both exceed 1 million transactions which is free. The
only answer that satisfies the above two criteria is answer C. Also, there does not seem to be an
urgency in speed of messaging therefore SQS satisfies that need. SNS being more real time
delivery mechanism.