The answer is to choose a memory-optimized instance family such as R6i. This is correct because the exhibit shows an application bottlenecked by high memory utilization, where performance degrades due to cache misses or excessive swap usage. A memory-optimized EC2 instance like R6i provides a higher ratio of RAM per vCPU, allowing the application to store more working data in memory and drastically reducing slow disk I/O, which directly improves performance without any code changes. On the SAA-C03 exam, this scenario tests your ability to match workload symptoms—like high swap or cache misses—to the correct instance family, with a common trap being to choose a compute-optimized instance when the real bottleneck is memory. Remember the mnemonic: "RAM the bottleneck? Go R-family."
SAA-C03 Design High-Performing Architectures Practice Question
This SAA-C03 practice question tests your understanding of design high-performing architectures. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
CloudWatch summary for app servers:
- Average CPUUtilization: 24%
- Average MemoryUtilization: 91%
- Average NetworkIn/Out: low
- Current instance type: m6i.large
- User reports: application slows when more sessions are active
Based on the exhibit, the team wants to improve application performance without changing the code. Which EC2 instance family should they choose next?
CloudWatch summary for app servers:
- Average CPUUtilization: 24%
- Average MemoryUtilization: 91%
- Average NetworkIn/Out: low
- Current instance type: m6i.large
- User reports: application slows when more sessions are active
A
Choose a compute-optimized instance family such as C6i to increase CPU performance.
Why wrong: Compute-optimized instances help when CPU is the bottleneck, but this workload shows low CPU usage and high memory usage.
B
Choose a memory-optimized instance family such as R6i to provide more RAM.
Memory-optimized instances are the best fit when memory pressure is causing slowdowns. The exhibit shows CPU is low while memory is consistently near saturation, which strongly suggests the application needs more RAM rather than more compute. Moving to an R6i family should reduce paging and improve response times without changing the application design.
C
Choose a storage-optimized instance family such as I4i to improve block storage throughput.
Why wrong: Storage-optimized instances are useful for high I/O workloads, but the exhibit does not show storage latency or throughput as the issue.
D
Choose a burstable instance family such as T3 to reduce cost and improve performance.
Why wrong: Burstable instances are not a good fix for sustained memory pressure. They are intended for variable, low-average CPU workloads, not memory shortages.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Choose a memory-optimized instance family such as R6i to provide more RAM.
The exhibit shows a memory-constrained application (e.g., high cache miss rates or swap usage) where performance is bottlenecked by insufficient RAM. Choosing a memory-optimized instance family like R6i provides more RAM per vCPU, allowing the application to keep more data in memory and reduce disk I/O, directly improving performance without code changes.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Choose a compute-optimized instance family such as C6i to increase CPU performance.
Why it's wrong here
Compute-optimized instances help when CPU is the bottleneck, but this workload shows low CPU usage and high memory usage.
✓
Choose a memory-optimized instance family such as R6i to provide more RAM.
Why this is correct
Memory-optimized instances are the best fit when memory pressure is causing slowdowns. The exhibit shows CPU is low while memory is consistently near saturation, which strongly suggests the application needs more RAM rather than more compute. Moving to an R6i family should reduce paging and improve response times without changing the application design.
Related concept
Read the scenario before looking for a memorised answer.
✗
Choose a storage-optimized instance family such as I4i to improve block storage throughput.
Why it's wrong here
Storage-optimized instances are useful for high I/O workloads, but the exhibit does not show storage latency or throughput as the issue.
✗
Choose a burstable instance family such as T3 to reduce cost and improve performance.
Why it's wrong here
Burstable instances are not a good fix for sustained memory pressure. They are intended for variable, low-average CPU workloads, not memory shortages.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume 'improve performance' always means faster CPU, but the exhibit's memory pressure metric (e.g., high swap usage or cache miss rate) directly points to RAM as the bottleneck, making memory-optimized instances the correct choice.
Trap categories for this question
Command / output trap
Compute-optimized instances help when CPU is the bottleneck, but this workload shows low CPU usage and high memory usage.
Detailed technical explanation
How to think about this question
Memory-optimized instances like R6i use high-frequency DDR5 memory and larger memory-to-vCPU ratios (e.g., 8 GiB per vCPU on r6i.large vs. 4 GiB on general-purpose m6i). Under the hood, the OS's page cache and application heap benefit from reduced swapping; the Linux 'kswapd' process will be less active, lowering latency. In a real-world scenario, a Java heap or in-memory database (e.g., Redis) would see fewer garbage collection pauses and higher throughput with more RAM.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Design High-Performing Architectures — This question tests Design High-Performing Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Choose a memory-optimized instance family such as R6i to provide more RAM. — The exhibit shows a memory-constrained application (e.g., high cache miss rates or swap usage) where performance is bottlenecked by insufficient RAM. Choosing a memory-optimized instance family like R6i provides more RAM per vCPU, allowing the application to keep more data in memory and reduce disk I/O, directly improving performance without code changes.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Based on the exhibit, the team wants to improve application performance without changing the code. Which EC2 instance family should they choose next?
easy
A.Choose a compute-optimized instance family such as C6i to increase CPU performance.
✓ B.Choose a memory-optimized instance family such as R6i to provide more RAM.
C.Choose a storage-optimized instance family such as I4i to improve block storage throughput.
D.Choose a burstable instance family such as T3 to reduce cost and improve performance.
Why B: The exhibit shows that the application is experiencing high memory utilization (e.g., memory pressure or swapping), which degrades performance. Choosing a memory-optimized instance family such as R6i provides more RAM per vCPU, directly addressing the bottleneck without requiring code changes. This improves application performance by reducing or eliminating swap usage and allowing more data to be cached in memory.
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Question Discussion
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