SOA-C02 Monitoring, Logging, and Remediation Practice Question
A company wants to monitor the health of its web application running on EC2 instances behind an Application Load Balancer (ALB). Which CloudWatch metric from the ALB can indicate that requests are failing due to server errors?
⚠ Common exam trap
Candidates often confuse HTTPCode_Target_5XX_Count with HTTPCode_ELB_5XX_Count, mistakenly thinking any 5xx error is from the target, when in fact the ELB can also generate 5xx errors (e.g., 502 from a malformed response) that are tracked separately.
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
✓
HTTPCode_Target_5XX_Count
The HTTPCode_Target_5XX_Count metric from the Application Load Balancer (ALB) specifically counts the number of HTTP response codes in the 5xx range returned by the target (EC2 instances). A 5xx status code indicates a server-side error, such as an internal server error (500), gateway timeout (504), or service unavailable (503), which directly reflects that requests are failing due to issues on the EC2 instances themselves.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
HTTPCode_Target_5XX_Count
Why this is correct
HTTPCode_Target_5XX_Count is the most direct health indicator because it counts responses from the target instances (EC2 containers or Lambda) where the application itself generated a server-side error, such as a 500 Internal Server Error or 503 Service Unavailable. A rising trend in this metric signals that the web application is experiencing failures processing requests, making it the ideal CloudWatch metric to alarm on for monitoring application health.
- ✗
HTTPCode_Target_4XX_Count
Why it's wrong here
HTTPCode_Target_4XX_Count tracks client-side errors like 404 Not Found or 401 Unauthorized. These errors are typically caused by malformed requests or invalid credentials sent by clients, not by underlying server or application problems, so they reflect request validity rather than the health of the web application.
- ✗
HTTPCode_Target_2XX_Count
Why it's wrong here
HTTPCode_Target_2XX_Count measures successful responses such as 200 OK, so it only confirms that the application is responding without errors. While a decrease in 2XX counts could suggest a problem, it is not a direct health metric because it does not capture failed requests; a perfectly healthy application should return 2XX for valid requests, making it less useful for detecting infrastructure or runtime failures.
- ✗
HTTPCode_Target_3XX_Count
Why it's wrong here
HTTPCode_Target_3XX_Count counts redirection responses like 301 Moved Permanently or 302 Found, which are normal HTTP behaviors that browsers follow to reach the correct resource. These responses do not indicate errors or health issues; they are a standard part of web traffic, so monitoring them provides little insight into the operational health of the application.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SOA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SOA-C02 exam.