PCD Integrating Google Cloud services Practice Question
Your application runs on Compute Engine and uses Cloud Pub/Sub to receive messages from a third-party service. Recently, the message delivery latency has increased significantly. The third-party reports no issues on their end. You notice that the Pub/Sub subscription's 'ackDeadlineSeconds' is set to 10. What is the most likely cause of the latency?
⚠ Common exam trap
Google Cloud often tests the distinction between push and pull subscriptions; the trap here is that candidates may incorrectly assume a push endpoint issue (Option C) without recognizing that the question implies a pull subscription by stating 'receives messages' rather than 'receives pushed messages'.
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
✓
The ackDeadlineSeconds is too short, causing frequent message redelivery.
A is correct because a 10-second ackDeadlineSeconds is very short. If your subscriber cannot process and acknowledge messages within 10 seconds, Pub/Sub will consider them unacknowledged and redeliver them. This redelivery causes duplicate processing and increases overall latency as messages are repeatedly sent back to the subscriber, delaying their final consumption.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The ackDeadlineSeconds is too short, causing frequent message redelivery.
Why this is correct
Short ack deadline leads to redelivery before processing completes.
- ✗
The topic's message retention duration is too long.
Why it's wrong here
Retention duration does not affect latency.
- ✗
The push endpoint is not responding, causing Pub/Sub to retry.
Why it's wrong here
The subscription is pull, not push.
- ✗
The subscription has an exponential backoff policy that is too aggressive.
Why it's wrong here
Exponential backoff would reduce retries.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.