SOA-C03 practice question: CloudWatch metrics, alarms and dashboards (1 of 3)

Monitoring, Logging, Analysis, Remediation, and Performance Optimization A free question from our original SOA-C03 practice exam. Try it, then open the answer to see why each option is right or wrong.

A regional bank's online banking team has separate CloudWatch alarms on its Application Load Balancer for HTTP 5xx error count and for target response time. Each alarm notifies the on-call engineer through Amazon SNS. Short spikes in one metric alone page the engineer several times a night, but every real outage so far has shown both metrics breaching together. The team wants one page only when both conditions are true at the same time. What should a CloudOps engineer do?

Choose one answer.

A. Raise the evaluation periods on both alarms to 10 so that brief spikes clear before either alarm reaches the ALARM state.
B. Create a composite alarm that requires both alarms to be in ALARM at the same time, and send the SNS notification only from the composite alarm.
C. Add an SNS subscription filter policy so that the engineer receives a message only when both alarms publish within the same minute.
D. Replace both alarms with anomaly detection alarms so that the thresholds adapt to normal nightly traffic patterns automatically.

Show the answer and explanation

Answer: B

A. Wrong: More evaluation periods smooth out short spikes, but each alarm still pages on its own whenever it breaches. The engineer would also be paged later for real outages, which slows the response. Learn more: Alarm evaluation (opens in a new tab)
B. Right: Correct. A composite alarm evaluates the states of other alarms with AND, OR and NOT. With actions removed from the underlying alarms, only the composite alarm pages, and only when both conditions hold together. Learn more: Combining alarms (opens in a new tab)
C. Wrong: SNS filter policies match attributes of a single message. They cannot correlate two separate messages or wait for a second alarm, so this cannot express the AND condition. Learn more: Amazon SNS message filtering (opens in a new tab)
D. Wrong: Anomaly detection builds a band of expected values for one metric. It can reduce false alarms on each metric, but the two alarms would still page separately rather than only when both breach. Learn more: Using CloudWatch anomaly detection (opens in a new tab)

Explanation

A composite alarm is the CloudWatch feature for alerting on a combination of conditions. Its rule expression, such as ALARM(errors) AND ALARM(latency), is evaluated against the states of the underlying alarms, and only the composite alarm needs actions. Tuning periods or thresholds on separate alarms reduces noise but never ties the two conditions together.

SOA-C03 practice question: CloudWatch metrics, alarms and dashboards (1 of 3)

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