The answer is a misconfigured alarm period of 5 minutes instead of 1 minute. This is correct because CloudWatch alarm evaluation windows are defined by the period setting multiplied by the number of consecutive periods; with a period of 5 minutes and 5 evaluation periods, the alarm requires 25 minutes of sustained breaching data to trigger, which explains why a 10-minute error spike was missed entirely. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how CloudWatch metric granularity and alarm period settings interact—a common trap is assuming the default 1-minute period is always used, when in fact the period can be manually set to a longer interval. Remember that ALB metrics publish every 1 minute by default, so if your alarm period is anything other than 1 minute, you are effectively stretching the evaluation window. A useful memory tip: "Period times Periods equals the total window you need to breach"—if the spike is shorter than that product, the alarm stays silent.
DOP-C02 Monitoring and Logging Practice Question
This DOP-C02 practice question tests your understanding of monitoring and logging. 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.
A company is running a critical web application on Amazon EC2 instances behind an Application Load Balancer (ALB) with Auto Scaling. The operations team notices that the application's error rate spiked for 10 minutes last night, but no CloudWatch alarm was triggered. The team has a CloudWatch alarm on the ALB's 'HTTPCode_Target_5XX_Count' metric with a threshold of 100 over 5 consecutive periods of 1 minute. What is the MOST likely reason the alarm did not trigger?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The alarm's period is set to 5 minutes instead of 1 minute.
Option A is correct because CloudWatch metrics are published at 1-minute granularity for ALB, and the alarm evaluates 5 consecutive periods (5 minutes) of data. The spike lasted 10 minutes, so the alarm should have triggered. However, if the alarm was created with a period of 5 minutes (not 1 minute), it would require 25 minutes of data to trigger, missing the 10-minute spike. Option B is incorrect because the ALB publishes metrics every 1 minute by default. Option C is incorrect because the ALB sends metrics to CloudWatch, not CloudWatch Logs. Option D is incorrect because the spike is for the target group, not the load balancer itself.
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.
✗
The ALB publishes metrics only at 5-minute granularity.
Why it's wrong here
ALB metrics are available at 1-minute granularity.
✗
The ALB sends metrics to CloudWatch Logs instead of CloudWatch Metrics.
Why it's wrong here
ALB sends metrics directly to CloudWatch Metrics.
✓
The alarm's period is set to 5 minutes instead of 1 minute.
Why this is correct
If the period is 5 minutes, the alarm would require data over 25 minutes to trigger, missing the 10-minute spike.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The alarm is configured on the wrong metric namespace.
Why it's wrong here
The metric is correctly in the AWS/ApplicationELB namespace.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which DOP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Monitoring and Logging — This question tests Monitoring and Logging — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The alarm's period is set to 5 minutes instead of 1 minute. — Option A is correct because CloudWatch metrics are published at 1-minute granularity for ALB, and the alarm evaluates 5 consecutive periods (5 minutes) of data. The spike lasted 10 minutes, so the alarm should have triggered. However, if the alarm was created with a period of 5 minutes (not 1 minute), it would require 25 minutes of data to trigger, missing the 10-minute spike. Option B is incorrect because the ALB publishes metrics every 1 minute by default. Option C is incorrect because the ALB sends metrics to CloudWatch, not CloudWatch Logs. Option D is incorrect because the spike is for the target group, not the load balancer itself.
What should I do if I get this DOP-C02 question wrong?
Identify which DOP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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