The answer is to set CloudWatch Logs retention to 90 days for all log groups and switch EC2 monitoring from detailed to basic except during incidents. This directly reduces recurring costs because CloudWatch Logs charges for storage beyond the retention period, and detailed EC2 monitoring incurs per-instance charges for one-minute metrics, whereas basic monitoring at five-minute intervals is free. On the SAA-C03 exam, this scenario tests your ability to separate audit-driven retention requirements from operational monitoring needs, a common trap being the assumption that all logs must be kept indefinitely or that detailed monitoring must run constantly. The key insight is that detailed monitoring is a metered, on-demand feature, not a permanent requirement. Remember the cost-saving mantra: keep logs only as long as auditors demand, and keep metrics only as granular as your current troubleshooting needs.
SAA-C03 Design Cost-Optimized Architectures Practice Question
This SAA-C03 practice question tests your understanding of design cost-optimized architectures. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 billing snapshot:
Logs ingestion: moderate
Logs storage: high
Custom metrics: low
Detailed monitoring charges: high
EC2 fleet:
200 instances across 4 Auto Scaling groups
Detailed monitoring enabled on every instance
CloudWatch Logs groups:
/app/prod/web: retention = Never Expire
/app/prod/api: retention = Never Expire
/app/prod/batch: retention = 365 days
Compliance note:
Keep logs available for at least 90 days
No requirement for 1-minute EC2 metrics on all instances
Based on the exhibit, the company wants to lower CloudWatch and EC2 monitoring costs. Auditors require logs to be retained for 90 days, but operations only uses detailed per-instance metrics during rare troubleshooting events. Which change best reduces recurring cost while preserving the required visibility?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
CloudWatch billing snapshot:
Logs ingestion: moderate
Logs storage: high
Custom metrics: low
Detailed monitoring charges: high
EC2 fleet:
200 instances across 4 Auto Scaling groups
Detailed monitoring enabled on every instance
CloudWatch Logs groups:
/app/prod/web: retention = Never Expire
/app/prod/api: retention = Never Expire
/app/prod/batch: retention = 365 days
Compliance note:
Keep logs available for at least 90 days
No requirement for 1-minute EC2 metrics on all instances
A
Disable CloudWatch Logs entirely and rely on application local files for 90 days.
Why wrong: Local files are not a durable or centralized substitute for CloudWatch Logs. This would increase operational risk, make retention harder to enforce, and reduce the team’s ability to search and audit logs across the fleet.
B
Increase the number of CloudWatch alarms so that metrics are collected less expensively.
Why wrong: Alarms do not reduce metric collection cost. The expensive part in the exhibit is detailed monitoring on every instance and indefinite log retention, neither of which is solved by adding more alarms.
C
Set CloudWatch Logs retention to 90 days for all log groups, and switch EC2 monitoring from detailed to basic except during incidents.
This directly addresses the two visible recurring cost drivers. Applying a 90-day retention policy stops indefinite log storage growth while still meeting the audit requirement. Basic monitoring is sufficient when 1-minute metrics are not required all the time, and detailed monitoring can be enabled selectively during incidents instead of paying for it across all 200 instances continuously.
D
Export all logs to Amazon S3 immediately and keep detailed monitoring enabled on every instance.
Why wrong: Exporting logs to S3 can help with archival economics, but it does not reduce the detailed monitoring charge, which is one of the largest costs in the exhibit. Keeping detailed monitoring on every instance preserves the major recurring cost driver.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set CloudWatch Logs retention to 90 days for all log groups, and switch EC2 monitoring from detailed to basic except during incidents.
Option C is correct because it directly addresses the two cost drivers: CloudWatch Logs storage costs are minimized by setting a 90-day retention policy (matching the audit requirement), and EC2 detailed monitoring (1-minute metrics) is replaced with basic monitoring (5-minute metrics) during normal operations, with the ability to switch back to detailed only when needed for troubleshooting. This preserves the required log retention and the ability to obtain high-resolution metrics on demand, while eliminating the recurring cost of storing logs indefinitely and paying for detailed monitoring on every instance.
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.
✗
Disable CloudWatch Logs entirely and rely on application local files for 90 days.
Why it's wrong here
Local files are not a durable or centralized substitute for CloudWatch Logs. This would increase operational risk, make retention harder to enforce, and reduce the team’s ability to search and audit logs across the fleet.
✗
Increase the number of CloudWatch alarms so that metrics are collected less expensively.
Why it's wrong here
Alarms do not reduce metric collection cost. The expensive part in the exhibit is detailed monitoring on every instance and indefinite log retention, neither of which is solved by adding more alarms.
✓
Set CloudWatch Logs retention to 90 days for all log groups, and switch EC2 monitoring from detailed to basic except during incidents.
Why this is correct
This directly addresses the two visible recurring cost drivers. Applying a 90-day retention policy stops indefinite log storage growth while still meeting the audit requirement. Basic monitoring is sufficient when 1-minute metrics are not required all the time, and detailed monitoring can be enabled selectively during incidents instead of paying for it across all 200 instances continuously.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Export all logs to Amazon S3 immediately and keep detailed monitoring enabled on every instance.
Why it's wrong here
Exporting logs to S3 can help with archival economics, but it does not reduce the detailed monitoring charge, which is one of the largest costs in the exhibit. Keeping detailed monitoring on every instance preserves the major recurring cost driver.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think increasing alarms or exporting logs to S3 reduces costs, but they fail to recognize that detailed monitoring is a per-instance hourly charge independent of alarms, and that S3 storage and API costs can exceed CloudWatch Logs costs if not managed carefully.
Detailed technical explanation
How to think about this question
CloudWatch detailed monitoring for EC2 charges $0.10 per instance per hour (for custom metrics) or $0.07 per instance per hour for standard detailed metrics, whereas basic monitoring is free. CloudWatch Logs charges $0.50 per GB ingested and $0.03 per GB stored per month; setting a retention policy of 90 days automatically deletes older log events, avoiding indefinite storage costs. The ability to enable detailed monitoring on the fly (via AWS CLI, SDK, or console) allows operations to switch to 1-minute granularity only during incidents, then revert to basic, achieving cost savings without losing troubleshooting capability.
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 Cost-Optimized Architectures — This question tests Design Cost-Optimized Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set CloudWatch Logs retention to 90 days for all log groups, and switch EC2 monitoring from detailed to basic except during incidents. — Option C is correct because it directly addresses the two cost drivers: CloudWatch Logs storage costs are minimized by setting a 90-day retention policy (matching the audit requirement), and EC2 detailed monitoring (1-minute metrics) is replaced with basic monitoring (5-minute metrics) during normal operations, with the ability to switch back to detailed only when needed for troubleshooting. This preserves the required log retention and the ability to obtain high-resolution metrics on demand, while eliminating the recurring cost of storing logs indefinitely and paying for detailed monitoring on every instance.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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