- A
Cloud Trace to trace message processing.
Why wrong: Tracing is useful for distributed context but not for measuring overall subscriber throughput; monitoring metrics are the first step.
- B
Cloud Monitoring to check subscriber's processing latency and throughput.
Cloud Monitoring has built-in metrics for Pub/Sub subscriptions, including 'subscriber latency' and 'sent messages count', which can confirm if the subscriber is too slow.
- C
Cloud Logging to view subscriber logs.
Why wrong: Logs may show errors or processing steps but do not directly measure throughput or latency; they are less efficient for diagnosing a backlog.
- D
Cloud Profiler to profile subscriber code.
Why wrong: Profiling can help optimize code but is a deeper analysis tool; for initial diagnosis, throughput metrics are more straightforward.
Quick Answer
The answer is Cloud Monitoring, because it provides the specific metrics needed to diagnose a Pub/Sub backlog caused by a slow subscriber. When messages accumulate, you need to examine subscriber processing latency and throughput, which Cloud Monitoring surfaces directly for each subscription. These metrics let you quantify exactly how slow the subscriber is and pinpoint whether the bottleneck is high latency per message or insufficient throughput capacity. On the Google Professional Cloud Developer exam, this question tests your understanding that Cloud Monitoring, not Logging or Debugging, is the diagnostic tool for performance metrics—a common trap is reaching for Cloud Logging to read logs, but logs won’t show you real-time processing rates or backlog size. Remember the mnemonic: “Latency and Throughput live in Monitoring” to avoid confusing observability tools.
PCD Managing application performance monitoring Practice Question
This PCD practice question tests your understanding of managing application performance monitoring. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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.
You deployed a new version of your application that uses Cloud Pub/Sub for asynchronous messaging. After deployment, you notice that messages are accumulating in the subscription backlog. You suspect the subscriber is too slow. Which tool should you use to diagnose?
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
Cloud Monitoring to check subscriber's processing latency and throughput.
Cloud Monitoring is the correct tool because it provides metrics such as subscriber processing latency, throughput, and backlog size for Pub/Sub subscriptions. By examining these metrics, you can quantify how slow the subscriber is and identify whether the issue is due to high latency or insufficient throughput, directly addressing the suspicion of a slow subscriber.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Cloud Trace to trace message processing.
Why it's wrong here
Tracing is useful for distributed context but not for measuring overall subscriber throughput; monitoring metrics are the first step.
- ✓
Cloud Monitoring to check subscriber's processing latency and throughput.
Why this is correct
Cloud Monitoring has built-in metrics for Pub/Sub subscriptions, including 'subscriber latency' and 'sent messages count', which can confirm if the subscriber is too slow.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Cloud Logging to view subscriber logs.
Why it's wrong here
Logs may show errors or processing steps but do not directly measure throughput or latency; they are less efficient for diagnosing a backlog.
- ✗
Cloud Profiler to profile subscriber code.
Why it's wrong here
Profiling can help optimize code but is a deeper analysis tool; for initial diagnosis, throughput metrics are more straightforward.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between monitoring (metrics) and tracing (request paths) — the trap here is that candidates confuse Cloud Trace's ability to trace individual messages with Cloud Monitoring's ability to aggregate subscriber performance metrics, leading them to pick Cloud Trace instead of Cloud Monitoring.
Trap categories for this question
Command / output trap
Logs may show errors or processing steps but do not directly measure throughput or latency; they are less efficient for diagnosing a backlog.
Detailed technical explanation
How to think about this question
Pub/Sub subscription metrics such as 'subscriber/processing_latency' and 'subscriber/throughput' are available in Cloud Monitoring and can be used to set alerting policies. A common subtle behavior is that if the subscriber's processing latency exceeds the subscription's acknowledgement deadline (default 10 seconds), messages may be redelivered, causing duplicate processing and further backlog growth. In a real-world scenario, a subscriber that makes external API calls may see latency spikes that are not visible in code profiling but are captured by Cloud Monitoring's latency metrics.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this PCD question test?
Managing application performance monitoring — This question tests Managing application performance monitoring — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Cloud Monitoring to check subscriber's processing latency and throughput. — Cloud Monitoring is the correct tool because it provides metrics such as subscriber processing latency, throughput, and backlog size for Pub/Sub subscriptions. By examining these metrics, you can quantify how slow the subscriber is and identify whether the issue is due to high latency or insufficient throughput, directly addressing the suspicion of a slow subscriber.
What should I do if I get this PCD question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This PCD practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCD exam.
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