PCA Practice Test 5 — 10 Questions

Question 1

Why are metric names required to follow a specific character set (e.g., alphanumeric and colons)?

Accepted Answer

For compatibility with PromQL. Prometheus metric names must match a regex to ensure they are compatible with the query language and internal storage format.

Answer

For faster scraping

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To save disk space

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To prevent duplicate metrics

Question 2

You are monitoring a legacy batch processing job that runs for only 30 seconds once every 24 hours. Which Prometheus component is necessary to collect these metrics?

Accepted Answer

Prometheus Pushgateway. Since the job is short-lived, Prometheus's standard scrape interval will likely miss it. The Pushgateway allows the job to push metrics before exiting.

Answer

Prometheus Exporter

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Prometheus Federation

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Prometheus Alertmanager

Question 3

Which file format does Prometheus use for its main configuration?

Accepted Answer

YAML. Prometheus configuration is strictly defined in YAML format.

Answer

XML

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JSON

Answer

TOML

Question 4

Which THREE labels are often considered part of the default Prometheus ecosystem metrics?

Accepted Answer

le. Option B (le) is correct because it is the standard label Prometheus attaches to histogram bucket series to indicate the inclusive upper bound of each bucket (e.g., le="0.5"), and it is essential for histogram_quantile() calculations. Option D (job) is correct because Prometheus automatically adds a job label to every scraped target, derived from the scrape configuration's job_name, identifying the logical service or scrape group. Option E (instance) is correct because Prometheus automatically attaches an instance label representing the specific target endpoint (host:port) that was scraped, distinguishing individual replicas within a job. Options A (group) and C (owner) are not part of the default Prometheus ecosystem labels; they are not injected by Prometheus during scraping and are not standard conventions used by PromQL functions or service discovery metadata.

Answer

group

Answer

owner

Question 5

When performing a vector-to-vector binary operation between two instant vectors of different label sets, which modifier allows matching on a subset of common labels?

Accepted Answer

on(...). The 'on(...)' modifier in PromQL allows vector-to-vector binary operations to match on a specified subset of labels, ignoring all other labels. When two instant vectors have different label sets, 'on(label1, label2)' restricts matching to only those labels, enabling the operation to proceed. This is the correct modifier for matching on a subset of common labels.

Answer

group_left(...)

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ignoring(...)

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matching(...)

Question 6

Which regular expression matcher selects all time series where the status label begins with the digit 5?

Accepted Answer

http_requests_total{status=~"^5.*"}. The =~ operator combined with a regular expression starting with ^5 matches labels beginning with 5.

Answer

http_requests_total{status=@"5*"}

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http_requests_total{status=^"5"}

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http_requests_total{status=~"5$"}

Question 7

Which THREE of the following are components of a Prometheus alert state?

Accepted Answer

inactive. In Prometheus, an alert rule transitions through three defined states: B. inactive, meaning the alert's expression evaluates to false and no alert is active; D. pending, meaning the expression has become true but the alert has not yet been true for the configured 'for' duration; and C. firing, meaning the condition has remained true for the full 'for' duration and the alert is now actively firing and sent to Alertmanager. These three states (inactive, pending, firing) are the complete set of alert states tracked by the Prometheus alerting engine. The unmarked options A. muted and E. sleeping are not Prometheus alert states; muting is an Alertmanager concept (silences/mute timers) applied to notifications, and 'sleeping' is not a Prometheus alert state at all.

Answer

muted

Answer

sleeping

Question 8

A team is transitioning from a traditional logging system to a metrics-based monitoring approach. Which category of observability data should the team prioritize to specifically identify the 'Latency' golden signal?

Accepted Answer

Time-series metrics. The 'Latency' golden signal is one of the four golden signals (latency, traffic, errors, saturation) defined in Google's SRE book. Latency is fundamentally a time-based measurement—how long a request takes to complete. Time-series metrics are specifically designed to capture numeric values over time, making them the ideal data category for tracking latency percentiles (e.g., p50, p95, p99) and alerting on thresholds. Metrics allow efficient aggregation and long-term trend analysis, which is essential for monitoring latency as a key performance indicator.

Answer

Infrastructure events

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Structured application logs

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Distributed traces

Question 9

Why does the 'rate()' function in PromQL behave unexpectedly on counter resets?

Accepted Answer

It detects the reset and ignores the wrap-around.. PromQL's rate() function is specifically designed to handle counter resets: when a counter decreases (indicating a process restart or counter wrap), rate() treats the drop as a reset and extrapolates the increase across the interval, effectively ignoring the wrap-around. This is why rate() is the recommended way to compute per-second rates on counters, rather than using deriv() or manual subtraction. The function assumes the counter only increases between resets and compensates accordingly.

Answer

It returns an error.

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It requires a manual offset.

Answer

It stops recording the metric.

Question 10

Which aggregation operator would you use to calculate the total sum of a metric across all instances?

Accepted Answer

sum(). The sum() aggregation operator in PromQL takes an instant vector and aggregates all matching time series into a single value by summing their current sample values. When applied across all instances of a metric (e.g., sum(node_cpu_seconds_total)), it produces the total across every series returned by the selector. This is exactly the semantics needed to compute a fleet-wide total of a metric.

Answer

avg_over_time()

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total()

Answer

count()