Practice Test Geeks(PCA) Prometheus Certified Associate Practice Test
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Prometheus Architecture & Components Flashcards

7 cards from real PCA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is the purpose of the Write-Ahead Log (WAL) in Prometheus's TSDB?

    Answer: To persist in-memory samples before they are compacted into blocks

    The WAL records incoming samples so that in-memory data can be recovered after a crash before it is written to immutable TSDB blocks.

  2. Which Prometheus feature allows writing samples simultaneously to an external system like Thanos or Cortex?

    Answer: Remote write

    Remote write forwards scraped samples in real time to a remote storage endpoint, enabling long-term storage and multi-tenant scenarios.

  3. What is a Prometheus 'target' in the context of its architecture?

    Answer: An HTTP endpoint Prometheus scrapes for metrics

    A target is an HTTP endpoint (typically /metrics) that Prometheus polls at each scrape interval to collect time-series samples.

  4. How does Prometheus handle high cardinality when scraping a target with millions of unique label combinations?

    Answer: It stores each unique label set as a separate time series, which can exhaust memory

    Each unique combination of metric name and label set is a distinct time series; too many unique combinations cause memory and CPU exhaustion known as a 'cardinality explosion'.

  5. In Prometheus architecture, what is the function of the 'notifier' component?

    Answer: It sends firing alerts from the rule evaluator to Alertmanager

    The notifier queues and dispatches pending alert notifications to one or more Alertmanager instances over HTTP.

  6. Which TSDB concept represents a contiguous on-disk directory containing immutable compressed samples for a fixed time range?

    Answer: Block

    A TSDB block is a directory (e.g., 01BX…) holding an index, chunks, and metadata for a specific time range, produced by compaction from the WAL.

  7. What happens to TSDB blocks when Prometheus's compaction process runs?

    Answer: Smaller blocks are merged into larger blocks to improve query performance

    Compaction merges multiple smaller time-range blocks into larger ones, reducing the number of files and improving read efficiency.