PCA Promql Practice Question
Which PromQL aggregator should be used to count the total number of active time series matching a selector?
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
✓
count(up)
The count operator counts the number of time series in an instant vector.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
count(up)
Why this is correct
Correct. count returns the number of series in the vector.
- ✗
sum(up)
Why it's wrong here
sum adds up the numerical values of the time series, not their quantity.
- ✗
len(up)
Why it's wrong here
len is not a valid PromQL aggregation operator.
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total(up)
Why it's wrong here
total is not a valid PromQL aggregation operator.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official CNCF / Linux Foundation exam blueprint
This PCA practice question is part of Courseiva's free CNCF / Linux Foundation 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 PCA exam.