Ambiguous question on Reserved Instances

[endian]

“57. Question

Category: CSAP – Cost Control

A pharmaceutical company has a hybrid cloud architecture in AWS. It has three different accounts for its environments: DEV, UAT, and PROD, which are all part of the consolidated billing account. The PROD account has purchased 10 r4.16xlarge Reserved EC2 Instances in the us-west-2a Availability Zone. Currently, there is no running EC2 instance in the PROD account because the application is not live yet but in the DEV account, there are 5 r4.16xlarge EC2 instances running in the us-west-2a Availability Zone. In the UAT account, there are also 5 r4.16xlarge EC2 instances running in the us-west-1a Availability Zone.

In this scenario, which account benefits the most out of the Reserved Instance pricing?”

This question is ambiguous because it does not specify whether the RIs are zonal or regional. If regional, the answer is ‘both accounts’. If zonal, the answer is ‘only the DEV account’

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/apply_ri.html
“A Reserved Instance that is purchased for a Region is called a regional Reserved Instance, and provides Availability Zone and instance size flexibility.

The Reserved Instance discount applies to instance usage in *any Availability Zone* in that Region.”

[Amiel-Palacol-TutorialsDojo]

Hi endian,

Thank you for the feedback.

The question stated that “the PROD account has purchased the Reserved Instance in the us-west-2a Availability Zone”, which is a keyword for zonal Reserved Instance. Specifying the scope of RI upfront will make the question look easy.

Please note that there are questions in the actual AWS exam that are difficult, tricky, and ambiguous. This is the style that we are trying to mimic in our practice tests. Some questions do not explicitly show the obvious keywords or phrases that will easily point to the answer.

Hope this helps.

Let us know if you need further assistance. The Tutorials Dojo team is dedicated to helping you pass your AWS exam!

Best regards,

Amiel Palacol @ Tutorials Dojo