Question

A SysOps administrator manages a fleet of application servers behind an Application Load Balancer. The team wants a single CloudWatch alarm that fires when the HTTP 5XX error rate exceeds 5% of total requests over a 5-minute period. Both the RequestCount and HTTPCode_Target_5XX_Count metrics are already published to CloudWatch. What is the MOST appropriate way to create this alarm?

Accepted Answer

Create a metric math expression that divides HTTPCode_Target_5XX_Count by RequestCount, multiplies by 100, and create an alarm on the resulting expression with a threshold of 5.

Answer

Create two separate alarms, one on HTTPCode_Target_5XX_Count and one on RequestCount, then combine them in a composite alarm using an AND rule.

Answer

Create a CloudWatch Logs metric filter on the ALB access logs to count 5XX responses and alarm when the count exceeds 5.

Answer

Enable anomaly detection on HTTPCode_Target_5XX_Count and set the alarm to trigger when values fall outside the expected band.