Question

A CloudOps engineer manages a fleet of application servers behind an Application Load Balancer. The team wants a single CloudWatch alarm that triggers when the HTTP 5XX error rate exceeds 5% of total requests, rather than alarming on a raw count of errors. Both HTTPCode_Target_5XX_Count and RequestCount metrics are available. 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, multiply by 100, and set the alarm threshold on the resulting expression at 5

Answer

Create a static alarm on HTTPCode_Target_5XX_Count with a threshold of 5 for one evaluation period

Answer

Enable CloudWatch anomaly detection on HTTPCode_Target_5XX_Count and alarm when the value is outside the expected band

Answer

Create a composite alarm combining separate alarms on HTTPCode_Target_5XX_Count and RequestCount