PCA Promql Practice Question
When writing a query with arithmetic operators, how does PromQL handle vector matching when both vectors have the exact same label sets?
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 performs a one-to-one match automatically based on identical label sets.
By default, PromQL performs a one-to-one match when the label sets of both vectors are identical.
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 ignores labels entirely and matches strictly based on metric names.
Why it's wrong here
PromQL matching evaluates full label sets, not just metric names.
- ✓
It performs a one-to-one match automatically based on identical label sets.
Why this is correct
Correct. Identical label sets match automatically in one-to-one operations.
- ✗
It throws a matching error unless the 'on' modifier is explicitly provided.
Why it's wrong here
Explicit modifiers are only required when label sets differ or when forcing specific matching behavior.
- ✗
It performs a cross-product join of all matching series.
Why it's wrong here
Cross-product joins require explicit many-to-many configurations.
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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.