KCNA Cloud Native Observability Practice Question
Which Prometheus metric type is used to represent a value that can increase or decrease over time, such as memory usage?
⚠ Common exam trap
KCNA often tests the distinction between metric types by presenting a scenario that seems like a counter (e.g., 'number of requests') but actually requires a gauge (e.g., 'current memory usage'), so candidates must carefully read whether the value can decrease.
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
✓
Gauge
A gauge is the Prometheus metric type designed to represent a value that can arbitrarily go up or down, such as memory usage, temperature, or current connections. Unlike counters, gauges are not monotonic and can be set to any value, making them ideal for instantaneous measurements. Memory usage fluctuates as processes allocate and free memory, so a gauge accurately captures this behavior.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Gauge
Why this is correct
A gauge holds a snapshot value that can rise or fall arbitrarily, matching memory usage sampled at scrape time. Unlike counters, which only increase (or reset), gauges support set, increment and decrement operations, making them the correct type for fluctuating measurements.
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Histogram
Why it's wrong here
Histograms bucket observations into cumulative ranges to support quantile calculation, so they cannot hold a single current memory value. They are tempting because they suit request-duration and response-size distributions, where aggregated bucket counts across many samples are the required output.
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Summary
Why it's wrong here
A summary samples observations over a sliding window and reports quantiles and counts; it does not hold a current value that rises and falls. Gauges represent values that can increase or decrease, such as memory usage. Summaries suit latency distributions and request-duration percentiles.
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Counter
Why it's wrong here
Counter values only increase or reset to zero on restart, so it cannot represent memory usage that falls as well as rises. It is tempting because counters correctly track cumulative totals such as requests served or bytes transmitted, where monotonic increase is the expected behaviour.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CNCF exam blueprint
This KCNA practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the KCNA exam.