Linux Foundation PCA glossary of Prometheus metrics, scraping, alerts, and observability terms.
Use this glossary when Prometheus Certified Associate (PCA) terms start to blur together. The goal is practical recognition, not encyclopedia coverage.
| Term | Exam meaning |
|---|---|
| Time series | Metric name plus label set over time. |
| Counter | Metric that only increases except reset. |
| Gauge | Metric that can increase or decrease. |
| Histogram | Metric type that records observations in buckets. |
| PromQL | Prometheus query language for selecting and calculating metrics. |
| Exporter | Component that exposes metrics in Prometheus format. |
| Pair | How to separate them |
|---|---|
| Metrics model vs PromQL | Ask which layer the scenario is testing, then match the answer to that layer only. |
| Control vs evidence | A control changes behavior; evidence proves behavior or supports investigation. |
| Managed service vs custom build | Managed services win for lower operational effort unless the requirement needs unsupported customization. |
| Prevention vs detection | Prevention blocks or reduces a bad event; detection finds or reports that it happened. |
Do not memorize terms in isolation. For each term, write one scenario where it is the best answer, one scenario where it is a distractor, and one signal that proves it worked.