- A
Use a single Cloud SQL for PostgreSQL instance with different schemas per service.
Why wrong: This does not achieve the goal of splitting the database; it's still a single database.
- B
Use BigQuery to store all data and query across services.
Why wrong: BigQuery is not designed for transactional workloads.
- C
Use Cloud SQL for PostgreSQL for each service and implement sagas to handle distributed transactions.
Sagas are the recommended pattern for maintaining data consistency across microservices.
- D
Use Cloud Spanner for all services to maintain ACID transactions across databases.
Why wrong: While Spanner provides ACID across databases, it couples services and contradicts microservices best practices.
Question 259 of 980
PCD Migrate Data Solutions Practice Question
This PCD practice question tests your understanding of migrate data solutions. 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 organization is planning a re-architect migration of a monolithic Oracle database to a microservices architecture using Cloud SQL for PostgreSQL and Cloud Spanner. They need to split the schema into multiple databases while maintaining data consistency across services. Which approach 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
✓
Use Cloud SQL for PostgreSQL for each service and implement sagas to handle distributed transactions.
For microservices, each service should own its database. To maintain consistency across services, they should implement compensating transactions (sagas) rather than distributed transactions. Cloud Spanner can be used if strong consistency is required across global scales, but for microservices, the pattern is to use eventual consistency with sagas.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 a single Cloud SQL for PostgreSQL instance with different schemas per service.
Why it's wrong here
This does not achieve the goal of splitting the database; it's still a single database.
- ✗
Use BigQuery to store all data and query across services.
Why it's wrong here
BigQuery is not designed for transactional workloads.
- ✓
Use Cloud SQL for PostgreSQL for each service and implement sagas to handle distributed transactions.
Why this is correct
Sagas are the recommended pattern for maintaining data consistency across microservices.
Related concept
Standard ACLs match source addresses.
- ✗
Use Cloud Spanner for all services to maintain ACID transactions across databases.
Why it's wrong here
While Spanner provides ACID across databases, it couples services and contradicts microservices best practices.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
- Standard ACLs match source addresses.
- Extended ACLs can match source, destination, protocol and ports.
- The first matching ACL entry is used.
- There is usually an implicit deny at the end.
TExam Day Tips
- Check inbound versus outbound direction.
- Read the ACL from top to bottom.
- Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCD ACL questions on filtering logic and placement.
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Migrate Data Solutions — study guide chapter
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FAQ
Questions learners often ask
What does this PCD question test?
Migrate Data Solutions — This question tests Migrate Data Solutions — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Use Cloud SQL for PostgreSQL for each service and implement sagas to handle distributed transactions. — For microservices, each service should own its database. To maintain consistency across services, they should implement compensating transactions (sagas) rather than distributed transactions. Cloud Spanner can be used if strong consistency is required across global scales, but for microservices, the pattern is to use eventual consistency with sagas.
What should I do if I get this PCD question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCD ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
About these practice questions
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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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