PCA Promql Practice Question
When performing a vector-to-vector binary operation between two instant vectors of different label sets, which modifier allows matching on a subset of common labels?
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
✓
on(...)
The on modifier restricts vector matching to a specified list of labels.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
group_left(...)
Why it's wrong here
group_left is used for many-to-one or one-to-many matching, not for selecting matching label keys.
- ✗
ignoring(...)
Why it's wrong here
The 'ignoring' modifier excludes specific labels from matching consideration, keeping all others.
- ✗
matching(...)
Why it's wrong here
matching is not a valid PromQL keyword modifier.
- ✓
on(...)
Why this is correct
Correct. The 'on' modifier restricts matching to the listed labels.
About these practice questions
This PCA question is part of Courseiva's 304-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.