KCNA Cloud Native Observability Practice Question
A company uses Prometheus for monitoring and wants to alert when the average CPU usage over 5 minutes exceeds 80%. Which PromQL query would correctly define this alert rule?
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
✓
avg(rate(node_cpu_seconds_total{mode!="idle"}[5m])) > 0.8
The query should calculate the average CPU usage rate over 5 minutes and compare it to 0.8 (80%).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
avg(rate(node_cpu_seconds_total{mode="idle"}[5m])) > 0.8
Why it's wrong here
This calculates the average idle rate, not usage.
- ✗
avg(node_cpu_seconds_total{mode!="idle"}[5m]) > 0.8
Why it's wrong here
Missing rate() function; node_cpu_seconds_total is a counter and needs rate() to get per-second rate.
- ✓
avg(rate(node_cpu_seconds_total{mode!="idle"}[5m])) > 0.8
Why this is correct
Correct. This calculates the average non-idle (usage) rate over 5 minutes and checks if >80%.
- ✗
sum(rate(node_cpu_seconds_total{mode!="idle"}[5m])) > 0.8
Why it's wrong here
Sum across all CPUs may exceed 1; avg is needed to get a fraction of total CPU.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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