SAA-C03 Design Cost-Optimized Architectures Practice Question
An EC2 workload runs in one region on a single instance type. For the last month, CloudWatch metrics show average CPU utilization of 12% and no sustained memory pressure. The team wants to reduce cost while maintaining the current performance level. What is the best first step?
⚠ Common exam trap
Many candidates think increasing instance size (Option B) is a safe 'performance buffer' move, but the question explicitly asks to reduce cost while maintaining current performance, making right-sizing via Compute Optimizer the logical first step.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use AWS Compute Optimizer to get recommendations for instance type and size changes.
AWS Compute Optimizer analyzes historical utilization metrics (CPU, memory, I/O) and provides actionable recommendations for right-sizing instances. Given the average CPU utilization of only 12% and no memory pressure, Compute Optimizer will likely recommend a smaller instance type or family that matches the workload's actual resource needs, reducing cost without affecting performance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use AWS Compute Optimizer to get recommendations for instance type and size changes.
Why this is correct
AWS Compute Optimizer analyzes historical metrics (such as CPU and memory utilization) and recommends instance type and size changes to improve cost-effectiveness while targeting performance. Given sustained low CPU and no sustained memory pressure, this is the most direct first step to identify a smaller/fewer-overprovisioned instance configuration that can maintain performance.
- ✗
Increase the instance size to reduce the risk of performance regression.
Why it's wrong here
If average CPU is already very low (12%) and there is no sustained memory pressure, increasing the instance size would likely increase cost without providing needed performance benefits. This directly contradicts the evidence of underutilization.
- ✗
Switch to Spot Instances immediately to reduce cost regardless of utilization.
Why it's wrong here
Switching to Spot could reduce cost, but the question’s evidence indicates a sizing/overprovisioning issue (low utilization). The best first step is to address the primary inefficiency—right sizing—before switching purchase models. Spot also introduces the possibility of interruptions, which is unnecessary if the workload can be optimized through sizing alone.
- ✗
Disable detailed monitoring to lower CloudWatch charges.
Why it's wrong here
Reducing monitoring cost is usually a minor optimization compared with compute savings. Also, detailed monitoring might still be needed to make accurate rightsizing decisions. The main cost driver indicated by the metrics is idle/overprovisioned compute, which requires sizing analysis rather than lowering monitoring granularity.
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