SOA-C02 Monitoring, Logging, and Remediation Practice Question

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_ELB_5XX_Count

  Why it's wrong here

  The HTTPCode_ELB_5XX_Count metric tracks HTTP 5xx errors generated by the Application Load Balancer itself, not by the EC2 targets. For example, a 503 is returned when the ALB has no healthy targets to route to, or a 502 occurs from an invalid response from the target. This metric is therefore not suitable for detecting application-level HTTP 5xx failures; it only reveals infrastructure-level load balancer problems.

• ✓

  HTTPCode_Target_5XX_Count

  Why this is correct

  The HTTPCode_Target_5XX_Count metric reports the number of HTTP 5xx responses returned directly by the registered EC2 instances, capturing errors such as 500 Internal Server Error from the application. Because these are the actual responses sent to clients from your web application, this metric is the correct measurement for an alarm that detects application-level failures. You can then create a CloudWatch alarm on this metric to trigger when the count exceeds a threshold, possibly combined with RequestCount to derive an error rate.

• ✗

  RequestCount

  Why it's wrong here

  The `RequestCount` metric tracks the total number of requests processed by the ALB, not the proportion of failed responses. To calculate an HTTP 5xx error rate exceeding 5%, you need a ratio metric (e.g., `HTTPCode_Target_5XX_Count` divided by `RequestCount`), which `RequestCount` alone cannot provide. It is tempting because it is a fundamental ALB metric often used for traffic volume monitoring, and in scenarios where you only need to detect a raw spike in request volume (e.g., a DDoS attack), `RequestCount` would be the correct choice.

• ✗

  TargetResponseTime

  Why it's wrong here

  TargetResponseTime measures the elapsed time from when the ALB sends the request to the target until it receives the complete response, or the time until the last byte received. It is a latency metric, not an error metric, so it cannot directly indicate HTTP 5xx responses from the application. While slow response times may correlate with errors or degraded performance, this metric does not provide the error count or rate required to alarm on HTTP 5xx failures.

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