- A
Use multiple subscriber instances to increase throughput.
Why wrong: Multiple subscribers can cause duplicates if not coordinated.
- B
Set the acknowledgement deadline to 600 seconds.
Why wrong: Deadline affects processing time but not exactly-once guarantee.
- C
Disable flow control to allow unlimited messages.
Why wrong: Flow control prevents overload but does not affect exactly-once.
- D
Enable message ordering on the subscription.
Ordering is required for exactly-once delivery as per Pub/Sub documentation.
- E
Set a maximum retention duration of 7 days.
Longer retention allows time for retries and deduplication.
Question 332 of 1,000
PCDE Exactly-once delivery Practice Question
This PCDE practice question tests your understanding of optimising service performance. 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: exactly-once delivery. 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.
A company uses Pub/Sub for event-driven processing and wants to ensure exactly-once delivery for critical messages. Which TWO configurations are required? (Choose two.)
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
✓
Enable message ordering on the subscription.
For exactly-once delivery in Google Cloud Pub/Sub, the only required configuration is to enable the 'exactly-once delivery' flag on the subscription. This option is not listed. Message ordering and maximum retention duration are not prerequisites for exactly-once delivery. None of the provided options are necessary for exactly-once delivery.
Key principle: Exactly-once delivery
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use multiple subscriber instances to increase throughput.
Why it's wrong here
Multiple subscribers can cause duplicates if not coordinated.
- ✗
Set the acknowledgement deadline to 600 seconds.
Why it's wrong here
Deadline affects processing time but not exactly-once guarantee.
- ✗
Disable flow control to allow unlimited messages.
Why it's wrong here
Flow control prevents overload but does not affect exactly-once.
- ✓
Enable message ordering on the subscription.
Why this is correct
Ordering is required for exactly-once delivery as per Pub/Sub documentation.
Related concept
Exactly-once delivery
- ✓
Set a maximum retention duration of 7 days.
Why this is correct
Longer retention allows time for retries and deduplication.
Related concept
Exactly-once delivery
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
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
- Exactly-once delivery
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
Exactly-once delivery
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. Exactly-once delivery 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.
Review exactly-once delivery, then practise related PCDE questions on the same topic to reinforce the concept.
- →
Optimising Service Performance — study guide chapter
Learn the concepts, then practise the questions
- →
Optimising Service Performance practice questions
Targeted practice on this topic area only
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Google Professional Cloud Database Engineer study guide
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FAQ
Questions learners often ask
What does this PCDE question test?
Optimising Service Performance — This question tests Optimising Service Performance — Exactly-once delivery.
What is the correct answer to this question?
The correct answer is: Enable message ordering on the subscription. — For exactly-once delivery in Google Cloud Pub/Sub, the only required configuration is to enable the 'exactly-once delivery' flag on the subscription. This option is not listed. Message ordering and maximum retention duration are not prerequisites for exactly-once delivery. None of the provided options are necessary for exactly-once delivery.
What should I do if I get this PCDE question wrong?
Review exactly-once delivery, then practise related PCDE questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Exactly-once delivery
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Last reviewed: Jul 4, 2026
This PCDE 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 PCDE exam.
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