PCA Promql Practice Question
You are joining an instant vector of application metrics with a static configuration instant vector containing target metadata using 'on(instance) group_right'. What does the 'group_right' modifier achieve?
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
✓
It allows the right-hand side to provide more time series than the left-hand side, keeping all right-hand side series and including matched left-hand side data.
In a many-to-one or one-to-many match, group_right causes the metric on the right-hand side to be included for every matching left-hand side, keeping all labels from the right side and supplementing them.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It reverses the vector matching direction to evaluate from right to left.
Why it's wrong here
Vector matching always evaluates from left to right; group_right controls cardinality expansion.
- ✓
It allows the right-hand side to provide more time series than the left-hand side, keeping all right-hand side series and including matched left-hand side data.
Why this is correct
group_right ensures that all series from the right-hand side are kept in the resulting vector, joined with matching left-hand side series.
- ✗
It drops all labels from the left-hand side vector.
Why it's wrong here
group_right keeps all labels from the right side and matching labels from the left.
- ✗
It ensures that the output contains only time series found exclusively on the right side.
Why it's wrong here
It still performs an inner or outer join depending on modifiers, but specifically populates based on the right-hand side cardinality.
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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.