- A
Cloud Spanner Change Streams
Change streams capture all mutations in a Spanner table and can be sent to Pub/Sub.
- B
Cloud Tasks
Why wrong: Cloud Tasks is for task queues, not streaming data replication.
- C
Dataflow
Dataflow can read from Pub/Sub with exactly-once semantics and write to Bigtable, performing any necessary transformations.
- D
Pub/Sub
Pub/Sub receives change stream events and can guarantee message ordering and exactly-once delivery to downstream subscribers.
- E
Cloud Functions
Why wrong: Cloud Functions is event-driven but not designed for high-throughput, ordered, exactly-once streaming.
Question 140 of 999
PCD Practice Question: Manage a Solution that Can Span Multiple Database Systems
This PCD practice question tests your understanding of manage a solution that can span multiple database systems. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
An e-commerce platform uses Cloud Spanner for order management and Bigtable for product recommendations. They need to replicate order changes to the Bigtable cluster in real-time for updating recommendations. The team must ensure that all order updates are captured and delivered exactly once, in order, to the Bigtable pipeline. Which THREE components should they use?
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 Spanner Change Streams
Spanner change streams capture all data changes (inserts, updates, deletes) and can publish to Pub/Sub. Dataflow can consume these messages and write to Bigtable with exactly-once processing. Pub/Sub provides ordered delivery when using message ordering. Cloud Tasks is not suitable for high-throughput streaming. Cloud Functions would be too slow and less reliable for exactly-once. BigQuery is not needed.
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 Spanner Change Streams
Why this is correct
Change streams capture all mutations in a Spanner table and can be sent to Pub/Sub.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Cloud Tasks
Why it's wrong here
Cloud Tasks is for task queues, not streaming data replication.
- ✓
Dataflow
Why this is correct
Dataflow can read from Pub/Sub with exactly-once semantics and write to Bigtable, performing any necessary transformations.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Pub/Sub
Why this is correct
Pub/Sub receives change stream events and can guarantee message ordering and exactly-once delivery to downstream subscribers.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Cloud Functions
Why it's wrong here
Cloud Functions is event-driven but not designed for high-throughput, ordered, exactly-once streaming.
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
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
What to study next
Got this wrong? Here's your next step.
Identify which PCD exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Questions learners often ask
What does this PCD question test?
Manage a Solution that Can Span Multiple Database Systems — This question tests Manage a Solution that Can Span Multiple Database Systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Cloud Spanner Change Streams — Spanner change streams capture all data changes (inserts, updates, deletes) and can publish to Pub/Sub. Dataflow can consume these messages and write to Bigtable with exactly-once processing. Pub/Sub provides ordered delivery when using message ordering. Cloud Tasks is not suitable for high-throughput streaming. Cloud Functions would be too slow and less reliable for exactly-once. BigQuery is not needed.
What should I do if I get this PCD question wrong?
Identify which PCD exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jul 4, 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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