Exams / SAA-C03 / Cost visibility and rightsizing / Question 1
SAA-C03 practice question: Cost visibility and rightsizing (1 of 2)
Design Cost-Optimized Architectures A free question from our original SAA-C03 practice exam. Try it, then open the answer to see why each option is right or wrong.
A company runs 200 Amazon EC2 instances that host in-memory Java services. The finance team suspects that many instances are oversized, but engineers warn that the services are limited by memory, not CPU, and that resizing based on CPU data alone has caused outages before. The company wants instance type recommendations based on several weeks of real usage, and it does not want to build its own analysis tooling. Which solution meets these requirements?
Choose one answer.
- AA. Opt in to AWS Compute Optimizer, and use its default analysis of the metrics that Amazon EC2 already sends to Amazon CloudWatch.
- BB. Opt in to AWS Compute Optimizer, and activate enhanced infrastructure metrics so that recommendations use up to 93 days of history.
- CC. Install the CloudWatch agent, and write an AWS Lambda function that compares each instance's memory use with instance type specifications.
- DD. Opt in to AWS Compute Optimizer, and install the Amazon CloudWatch agent on the instances to publish memory utilisation metrics.
Show the answer and explanation
Answer: D
- A. Wrong: Compute Optimizer is the right service for right-sizing recommendations, but EC2 does not report memory use to CloudWatch by itself. Without memory data, recommendations rest on CPU, network and disk metrics, which is the CPU-only resizing the engineers warned about. Learn more: What is AWS Compute Optimizer? (opens in a new tab)
- B. Wrong: Enhanced infrastructure metrics is a paid feature that extends the lookback period from 14 days to up to 93 days. A longer history does not add memory data, so the recommendations would still be blind to the services' real limit. Memory needs the CloudWatch agent. Learn more: Enhanced infrastructure metrics (opens in a new tab)
- C. Wrong: This would capture memory use, but the company would have to build and maintain the comparison logic, pricing data and reports itself. That is the in-house analysis tooling it wants to avoid, when Compute Optimizer already does this analysis. Learn more: EC2 instance metrics analysed by Compute Optimizer (opens in a new tab)
- D. Right: Correct. Compute Optimizer analyses each instance's utilisation history and recommends better-fitting instance types. Once the CloudWatch agent publishes memory utilisation with the InstanceId dimension, Compute Optimizer includes memory in its analysis, so recommendations reflect the real constraint. Learn more: EC2 instance metrics analysed by Compute Optimizer (opens in a new tab)
Explanation
AWS Compute Optimizer gives right-sizing recommendations without custom tooling, and by default it looks at 14 days of history, which covers several weeks of real use. It can only consider memory if memory metrics exist, and EC2 does not publish them by default, so the CloudWatch agent must be installed. Extending the lookback period does not fix the missing memory data.
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