PCA Practice Exam 3 — 20 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.

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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.

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XML

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JSON

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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.

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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.

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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.

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It returns an error.

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It requires a manual offset.

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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()

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count()

Question 11

A system is experiencing high latency. You need to identify if the latency is caused by external dependencies. Which of the Four Golden Signals is most relevant for this discovery?

Accepted Answer

Latency. Latency, one of the Four Golden Signals, measures the time it takes to service a request, and it is the signal explicitly designed to reveal slow responses. By breaking latency down by dependency (e.g., downstream API, database, third-party service), you can determine whether external dependencies are the source of the slowdown. This makes Latency the most relevant signal for diagnosing high-latency issues.

Answer

Errors

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Saturation

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Traffic

Question 12

When writing a custom exporter in Python, what is the most common way to expose the metrics?

Accepted Answer

Using start_http_server(). The prometheus_client library provides a start_http_server() method to expose metrics on a specified port.

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Writing to a file

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Using a message queue

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Using a database connection

Question 13

Which TWO are common types of Prometheus exporters?

Accepted Answer

Node Exporter. Node Exporter (A) is a canonical Prometheus exporter that runs on a host and exposes hardware and OS metrics such as CPU, memory, disk, filesystem, and network statistics on /metrics for Prometheus to scrape. Blackbox Exporter (D) is also a standard Prometheus exporter, but it probes external endpoints over HTTP, HTTPS, DNS, TCP, and ICMP and converts the results into Prometheus metrics, making it ideal for availability and latency monitoring. The other options are not established Prometheus exporter types: there is no standard "Log Exporter" (B) since logs are handled by Loki/Promtail rather than Prometheus, "Push Exporter" (C) is not a real exporter type because Prometheus uses the Pushgateway for push-based metrics rather than a push exporter, and "Trace Exporter" (E) relates to distributed tracing systems like OpenTelemetry/Jaeger, not Prometheus metrics collection.

Answer

Log Exporter

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Push Exporter

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Trace Exporter

Question 14

Which Grafana panel type is best for showing a trend of a metric over time?

Accepted Answer

Time series. The Time series panel is the standard for plotting metrics over time.

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Table

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Stat

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Bar gauge

Question 15

An application is emitting logs that contain '5xx' status codes when a service is unavailable. If you want to create an alert that triggers based on the rate of these errors, what is the best practice for observability?

Accepted Answer

Expose a metric incrementing on every 5xx error and alert on the rate of that metric.. Logs are useful for root cause analysis, but for alerting on rates, you should convert the error occurrence into a metric increment, as metrics are more efficient for long-term calculation and alerting.

Answer

Alert directly on the log stream using a log aggregator.

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Use Prometheus to scrape the log file directly.

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Increase log verbosity to trace the request until the error is resolved.

Question 16

You are using the blackbox_exporter to monitor an HTTP endpoint. Which module configuration is required to check the HTTP status code?

Accepted Answer

http_2xx. The http_2xx module is the standard configuration for checking that an endpoint returns a successful HTTP status code.

Answer

dns_query

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tcp_connect

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icmp_ping

Question 17

If you are using a Histogram, what is the purpose of the '_sum' metric?

Accepted Answer

To store the sum of observations. The _sum metric provides the sum of all observed values, which allows calculating the average when combined with the _count metric.

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To store the median

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To store the maximum value

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To store the total count

Question 18

What happens if a label set for a metric changes during its lifetime?

Accepted Answer

A new time series is created. Changing a label set creates a brand new time series in Prometheus.

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An error is logged

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The series is updated in-place

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The metric is deleted

Question 19

What is the purpose of the 'rule_files' configuration?

Accepted Answer

To define alerting and recording rules. rule_files point to recording and alerting rules that Prometheus evaluates.

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To manage user authentication

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To define static targets

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To configure global retention

Question 20

Which annotation is commonly used to provide a human-readable description in an alert?

Accepted Answer

description. The 'summary' or 'description' annotations are standard practices for providing context in alert notifications.

Answer

severity

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instance

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job