- A
Set the environment variable TRACE_SAMPLE_RATE to a value between 0 and 1.
Setting the environment variable 'TRACE_SAMPLE_RATE' is not correct; Cloud Run uses OpenTelemetry environment variables 'OTEL_TRACES_SAMPLER' and 'OTEL_TRACES_SAMPLER_ARG' to control sampling rate. This option is partially correct in concept but uses the wrong variable names.
- B
Disable Cloud Trace and use only Cloud Monitoring metrics.
Why wrong: Disabling Cloud Trace removes observability entirely and is not a recommended approach to reduce sampling costs.
- C
Modify the Cloud Trace API quota to limit trace ingestion.
Why wrong: Modifying Cloud Trace API quota limits the volume of trace ingestion, not the sampling rate. This could reduce costs but does not directly control the sampling probability.
- D
Configure the trace sampling rate in the Cloud Monitoring alert policy.
Why wrong: Cloud Monitoring alert policies are used for alerting, not for configuring trace sampling rates.
PCDE OpenTelemetry Practice Question
This PCDE practice question tests your understanding of implementing service monitoring strategies. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. A key principle to apply: openTelemetry. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An application running on Cloud Run is automatically instrumented with Cloud Trace, but the trace sampling rate is too high, causing excessive costs. How can the engineer reduce the sampling rate?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Set the environment variable TRACE_SAMPLE_RATE to a value between 0 and 1.
To reduce the trace sampling rate in Cloud Run, set the OpenTelemetry environment variables: OTEL_TRACES_SAMPLER to 'traceidratio' and OTEL_TRACES_SAMPLER_ARG to a value between 0 and 1 (e.g., '0.1' for 10% sampling). The option 'TRACE_SAMPLE_RATE' is not a recognized variable in Cloud Run; the correct approach uses OpenTelemetry configuration.
Key principle: OpenTelemetry
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Set the environment variable TRACE_SAMPLE_RATE to a value between 0 and 1.
Why this is correct
Setting the environment variable 'TRACE_SAMPLE_RATE' is not correct; Cloud Run uses OpenTelemetry environment variables 'OTEL_TRACES_SAMPLER' and 'OTEL_TRACES_SAMPLER_ARG' to control sampling rate. This option is partially correct in concept but uses the wrong variable names.
Related concept
OpenTelemetry
- ✗
Disable Cloud Trace and use only Cloud Monitoring metrics.
Why it's wrong here
Disabling Cloud Trace removes observability entirely and is not a recommended approach to reduce sampling costs.
- ✗
Modify the Cloud Trace API quota to limit trace ingestion.
Why it's wrong here
Modifying Cloud Trace API quota limits the volume of trace ingestion, not the sampling rate. This could reduce costs but does not directly control the sampling probability.
- ✗
Configure the trace sampling rate in the Cloud Monitoring alert policy.
Why it's wrong here
Cloud Monitoring alert policies are used for alerting, not for configuring trace sampling rates.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates may mistakenly use a generic environment variable like 'TRACE_SAMPLE_RATE' instead of the OpenTelemetry-specific variables required by Cloud Run.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- OpenTelemetry
- OTEL_TRACES_SAMPLER
- OTEL_TRACES_SAMPLER_ARG
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
OpenTelemetry
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Review openTelemetry, then practise related PCDE questions on the same topic to reinforce the concept.
- →
Implementing Service Monitoring Strategies — study guide chapter
Learn the concepts, then practise the questions
- →
Implementing Service Monitoring Strategies practice questions
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FAQ
Questions learners often ask
What does this PCDE question test?
Implementing Service Monitoring Strategies — This question tests Implementing Service Monitoring Strategies — OpenTelemetry.
What is the correct answer to this question?
The correct answer is: Set the environment variable TRACE_SAMPLE_RATE to a value between 0 and 1. — To reduce the trace sampling rate in Cloud Run, set the OpenTelemetry environment variables: OTEL_TRACES_SAMPLER to 'traceidratio' and OTEL_TRACES_SAMPLER_ARG to a value between 0 and 1 (e.g., '0.1' for 10% sampling). The option 'TRACE_SAMPLE_RATE' is not a recognized variable in Cloud Run; the correct approach uses OpenTelemetry configuration.
What should I do if I get this PCDE question wrong?
Review openTelemetry, then practise related PCDE questions on the same topic to reinforce the concept.
What is the key concept behind this question?
OpenTelemetry
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Last reviewed: Jul 4, 2026
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