Free Prometheus Certified Associate (PCA) Practice Questions

Sample Practice Questions

Try these 10 sample questions from the Prometheus Certified Associate (PCA) practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1What is the primary purpose of metrics as an observability signal?

   1. A. To provide aggregate statistical information about a system
   2. B. To preserve the text of each individual application event
   3. C. To reconstruct the sequence of spans for one request
   4. D. To capture the complete payload of each network exchange

   Answer: A

   Explanation: The documentation states, "metrics are intended to provide statistical information in aggregate." Metrics summarize system behavior; individual event records, request paths, and packet payloads serve different purposes.

   Reference: Metrics | OpenTelemetry — Metric instruments and aggregation

2. 2Which Prometheus component stores the samples collected from instrumented jobs?

   1. A. The Alertmanager notification service
   2. B. The main Prometheus server
   3. C. The application's client library
   4. D. The Grafana dashboard service

   Answer: B

   Explanation: The component list identifies "the main Prometheus server" as the component "which scrapes and stores time series data". Client libraries expose instrumentation, Alertmanager handles alerts, and Grafana visualizes data.

   Reference: Overview | Prometheus — Components — main Prometheus server

3. 3Which selector returns only http_requests_total series whose job is exactly api and whose environment is exactly prod?

   1. A. http_requests_total{job="api",environment!="prod"}
   2. B. http_requests_total{job=~"api|worker",environment="prod"}
   3. C. http_requests_total{environment="prod",job="api"}
   4. D. http_requests_total{environment=~"prod|staging",job="api"}

   Answer: C

   Explanation: The selector documentation defines equality as "Select labels that are exactly equal to the provided string." Comma-separated matchers must all pass. Requiring environment equal to prod and job equal to api implements the requested conjunction. The other selectors exclude prod or permit extra jobs or environments through regex alternatives.

   Reference: Querying basics | Prometheus — Time series selectors — Instant vector selectors — label matching

4. 4What capability does a language-matched Prometheus client library provide when instrumenting an application's code?

   1. A. Discover remote scrape targets and schedule their server-side scrapes
   2. B. Define metric types and expose internal metrics through an HTTP endpoint
   3. C. Evaluate PromQL against retained history and persist recording-rule results
   4. D. Group firing alerts and deliver notifications through receiver integrations

   Answer: B

   Explanation: The documentation says client libraries "implement the Prometheus metric types" and let you "define and expose internal metrics via an HTTP endpoint". This is application instrumentation. Server-side discovery, historical PromQL evaluation, and Alertmanager notification delivery are different ecosystem responsibilities.

   Reference: Client libraries | Prometheus — Client libraries — introduction and language selection

5. 5A Grafana dashboard will query an existing Prometheus server. Which service URL belongs in its Prometheus data source configuration?

   1. A. The Alertmanager service URL
   2. B. The Pushgateway service URL
   3. C. The Prometheus server URL
   4. D. The Node Exporter service URL

   Answer: C

   Explanation: The integration guide instructs, "Set the appropriate Prometheus server URL". Grafana queries Prometheus for stored metrics; the notification service, push intermediary, and host exporter are different components.

   Reference: Grafana | Prometheus — Creating a Prometheus data source

6. 6Which metric instrument represents a total that accumulates as new events occur, such as the number of requests processed?

   1. A. Gauge
   2. B. Histogram
   3. C. Counter
   4. D. UpDownCounter

   Answer: C

   Explanation: The instrument list describes "Counter: A value that accumulates over time". A counter records increasing totals; a gauge records a current value, a histogram aggregates distributions, and an UpDownCounter also allows decreases.

   Reference: Metrics | OpenTelemetry — Metric instruments — Counter

7. 7A dashboard repeatedly executes an expensive PromQL expression. Which Prometheus mechanism can precompute the expression and store its result as new time series?

   1. A. A service-discovery configuration
   2. B. An Alertmanager notification template
   3. C. A target label-rewriting rule
   4. D. A recording rule

   Answer: D

   Explanation: The documentation states, "Recording rules allow you to precompute frequently needed or computationally expensive expressions and save their result as a new set of time series." Discovery and relabeling configure targets; notification templates format alerts rather than storing query results.

   Reference: Defining recording rules | Prometheus — Recording rules

8. 8Which environment label value matches the PromQL matcher environment=~"prod"?

   1. A. prod
   2. B. production
   3. C. preprod
   4. D. prod-east

   Answer: A

   Explanation: The documentation states, "Regex matches are fully anchored." Thus this expression matches the entire value prod, not a value that merely starts with or contains that text.

   Reference: Querying basics | Prometheus — Instant vector selectors — regular-expression matching

9. 9When Prometheus scrapes an application's client-library HTTP endpoint, what does the library send?

   1. A. The current state of the tracked metrics
   2. B. Only metric increments since the previous scrape
   3. C. A chronological log of every instrumented event
   4. D. Only metrics that exceeded an alert threshold

   Answer: A

   Explanation: The client library page states that the library "sends the current state of all tracked metrics to the server." The scrape does not imply delta-only transmission, an event log, or threshold filtering.

   Reference: Client libraries | Prometheus — Client libraries — scrape behavior

10. 10In the Grafana Prometheus query editor's Custom legend field, which template substitutes each returned series' method and status label values?

    1. A. {{method}} - {{status}}
    2. B. ${method:raw} - ${status:raw}
    3. C. {{ $labels.method }} - {{ $labels.status }}
    4. D. ${__field.labels.method} - ${__field.labels.status}

    Answer: A

    Explanation: The Grafana query editor documentation states, "{{hostname}} is replaced with the value of the hostname label." The same Custom legend syntax substitutes method and status. The raw format applies to dashboard-variable interpolation, $labels is the Prometheus alert-template namespace, and __field.labels expressions belong to a panel field's Display name option rather than this query editor legend field.

    Reference: Prometheus query editor | Grafana documentation — Query options — Legend — Custom