PCA Observability Concepts — 25 Questions

Question 1

Which component is strictly required to monitor batch jobs in a Prometheus ecosystem?

Accepted Answer

Pushgateway. The Pushgateway is specifically designed to allow ephemeral batch jobs to push metrics, which Prometheus then pulls.

Answer

Grafana

Answer

Alertmanager

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PromQL

Question 2

You are deploying Prometheus in a cluster with highly dynamic ephemeral pods. Which concern is the most significant regarding cardinality?

Accepted Answer

The memory overhead of storing time series with unique label sets.. High cardinality arises from labels with high-variance values, which can lead to memory exhaustion in the Prometheus TSDB.

Answer

The network bandwidth used by the pushgateway.

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The disk space used by WAL logs.

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The number of targets being scraped.

Question 3

You notice that your Prometheus instance memory usage is growing linearly despite constant traffic. What is the most likely cause?

Accepted Answer

Increasing metric cardinality.. If cardinality (unique label combinations) increases over time, the number of active time series keeps growing, increasing RAM usage.

Answer

CPU throttling.

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Network latency.

Answer

Too many alert rules.

Question 4

In the context of the Four Golden Signals, what does 'Saturation' measure?

Accepted Answer

The amount of queued work.. Saturation measures how 'full' a service is, typically defined by identifying the most constrained resource (e.g., CPU, RAM, or disk IO).

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The number of 5xx errors.

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The speed of the network.

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The number of successful requests.

Question 5

A legacy batch job runs once per day and finishes in seconds. Why is a standard Prometheus pull model inadequate here?

Accepted Answer

The job is too fast for HTTP polling.. Prometheus pull intervals are typically set to seconds or minutes; a job that finishes quickly might never be 'up' when Prometheus scrapes it.

Answer

The data is too large for memory.

Answer

Pull model is insecure.

Answer

Prometheus cannot scrape batch jobs.

Question 6

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 measures the time it takes to service a request, which directly indicates performance issues in dependencies.

Answer

Errors

Answer

Saturation

Answer

Traffic

Question 7

What is the primary drawback of using the Pushgateway for long-running services?

Accepted Answer

It bypasses Prometheus's liveness check for the source.. Using the Pushgateway removes the 'up' status check that Prometheus performs on targets, and it can become a bottleneck or single point of failure.

Answer

It requires manual restarts.

Answer

It lacks metric persistence.

Answer

Prometheus cannot query the Pushgateway.

Question 8

An SRE team is transitioning from traditional logs to metrics for performance monitoring. Which scenario best justifies using metrics over logs?

Accepted Answer

Tracking the request rate per second on a web server.. Metrics are numerical representations of data measured over time, making them efficient for time-series analysis and alerting, whereas logs are better for debugging specific events.

Answer

Auditing user access attempts for compliance.

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Storing the payload of a failed transaction for later inspection.

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Recording the stack trace of a Java application crash.

Question 9

What is the primary difference between a metric and a log?

Accepted Answer

Metrics represent snapshots of state; logs represent discrete events.. Metrics are aggregated, numeric data points over time, while logs are timestamped records of specific events.

Answer

Metrics are for debugging; logs are for alerting.

Answer

Logs are cheaper to store.

Answer

Logs are always real-time.

Question 10

Which golden signal would you monitor to detect if a specific API endpoint is returning 404s?

Accepted Answer

Errors. The 'Errors' signal tracks the rate of failed requests, including HTTP 4xx and 5xx codes.

Answer

Traffic

Answer

Saturation

Answer

Latency

Question 11

When configuring Service Discovery in Kubernetes, why might you use relabeling?

Accepted Answer

To reduce cardinality by dropping high-variance labels.. Relabeling is used to modify, drop, or keep metrics based on label values, which is essential for managing cardinality and filtering unwanted data.

Answer

To encrypt metric traffic.

Answer

To increase scrape frequency.

Answer

To store logs in Prometheus.

Question 12

Why are traces considered distinct from metrics in observability?

Accepted Answer

Traces track individual request lifecycles through services.. Traces provide context on a single request's path through a distributed system, whereas metrics provide aggregated health status.

Answer

Traces are always numeric.

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Traces are only for frontend applications.

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Metrics replace traces.

Question 13

Which monitoring philosophy is core to the Prometheus architecture?

Accepted Answer

Centralized pull-based scraping.. Prometheus favors the pull model, where the server controls the scrape rate and frequency, providing better control over the load on the monitoring system.

Answer

Agent-less log aggregation.

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Push-based data ingestion.

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Event-driven architecture.

Question 14

What is the primary benefit of using a pull-based model for monitoring?

Accepted Answer

The Prometheus server can detect target failure.. The pull model allows the monitoring server to detect when a target is down and prevents the target from overwhelming the monitoring system.

Answer

It supports higher data throughput.

Answer

It is easier to configure for firewalls.

Answer

It avoids network security issues.

Question 15

You are seeing 'Too many active series' in your Prometheus logs. Which action should be your first priority to address this?

Accepted Answer

Analyze the number of active series per label name.. Identifying which labels are causing the high cardinality is the standard first step to prevent OOM (Out Of Memory) crashes.

Answer

Switch to a different monitoring tool.

Answer

Disable all alerting rules.

Answer

Increase Prometheus memory limits.

Question 16

A developer adds a 'user_id' label to an HTTP request counter. What is the operational risk?

Accepted Answer

High cardinality will consume excessive memory.. Adding a high-cardinality dimension like 'user_id' can explode the number of time series created, crashing the TSDB.

Answer

The query speed will increase.

Answer

Prometheus will reject the metric.

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The metric will stop recording.

Question 17

Which of these is considered a 'counter' in Prometheus?

Accepted Answer

Total number of HTTP requests processed.. A counter is a cumulative metric that only ever goes up, used for things like request totals.

Answer

Temperature of a server room.

Answer

Average latency over 5 minutes.

Answer

Current memory usage of a process.

Question 18

What is the purpose of a Gauge metric?

Accepted Answer

To track values that fluctuate up and down.. A gauge represents a single numerical value that can arbitrarily go up and down, such as temperature or memory usage.

Answer

To track request rates.

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To track job start times.

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To track request durations.

Question 19

When designing a monitoring strategy, why should you avoid monitoring 'everything'?

Accepted Answer

It leads to signal noise and high resource costs.. Excessive metric collection leads to high storage costs, increased query latency, and signal-to-noise ratio degradation (alert fatigue).

Answer

Logs are always better for everything.

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The network will be saturated.

Answer

Prometheus cannot handle many metrics.

Question 20

What is the primary role of the 'Alertmanager'?

Accepted Answer

To manage and route alerts generated by Prometheus.. Alertmanager is responsible for grouping, silencing, and routing alerts to external systems like PagerDuty or email.

Answer

To store long-term metric data.

Answer

To scrape metrics from targets.

Answer

To visualize metrics in dashboards.