The answer is to use Database Migration Service (DMS) with continuous replication. This strategy is correct because DMS leverages change data capture (CDC) to continuously replicate ongoing transactions from the source PostgreSQL database to Cloud SQL, maintaining near-zero lag and allowing the application to remain fully operational throughout the migration. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of minimizing downtime during live migrations; a common trap is selecting a one-time dump-and-load method like pg_dump or a logical replication setup that requires manual configuration, both of which introduce significant downtime. The key insight is that DMS handles the CDC plumbing automatically, enabling a cutover that takes seconds by simply stopping writes to the source and promoting the target. Memory tip: think “CDC = Continuous Data Cutover” to recall that continuous replication is the only approach that achieves near-zero downtime for PostgreSQL migrations to Cloud SQL.
PCDE Plan and manage database infrastructure Practice Question
This PCDE practice question tests your understanding of plan and manage database infrastructure. 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.
A company is migrating a PostgreSQL database to Cloud SQL for PostgreSQL. They want to ensure minimal downtime during the migration. Which migration strategy should they use?
Set up application-level dual writes to both databases and switch over
Why wrong: Dual writes are complex, require application changes, and risk data inconsistency.
B
Use Database Migration Service (DMS) with continuous replication
DMS provides minimal downtime via change data capture and replication.
C
Create a read replica in Cloud SQL and promote it
Why wrong: Creating a read replica from an external primary is not directly supported; it requires setting up external replication manually and may have significant downtime.
D
Export the database using pg_dump and import into Cloud SQL
Why wrong: pg_dump export/import requires downtime and is not continuous.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use Database Migration Service (DMS) with continuous replication
Database Migration Service (DMS) with continuous replication is the correct strategy because it uses change data capture (CDC) to replicate ongoing transactions from the source PostgreSQL database to Cloud SQL with minimal lag. This allows the application to remain fully operational during the migration, and the cutover can be performed in seconds by stopping writes to the source and promoting the target, achieving near-zero downtime.
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.
✗
Set up application-level dual writes to both databases and switch over
Why it's wrong here
Dual writes are complex, require application changes, and risk data inconsistency.
✓
Use Database Migration Service (DMS) with continuous replication
Why this is correct
DMS provides minimal downtime via change data capture and replication.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a read replica in Cloud SQL and promote it
Why it's wrong here
Creating a read replica from an external primary is not directly supported; it requires setting up external replication manually and may have significant downtime.
✗
Export the database using pg_dump and import into Cloud SQL
Why it's wrong here
pg_dump export/import requires downtime and is not continuous.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'read replica promotion' (which only works within Cloud SQL) with cross-environment migration, or they assume that pg_dump can be used with minimal downtime by running it on a replica, but the export still locks tables or requires a consistent snapshot that interrupts writes.
Detailed technical explanation
How to think about this question
DMS leverages PostgreSQL's logical replication slots and the pgoutput plugin to capture changes in real time without requiring triggers or application changes. During the continuous replication phase, DMS maintains a consistent snapshot and applies incremental changes; the final cutover involves stopping writes to the source, waiting for replication lag to reach zero, and promoting the Cloud SQL instance as the new primary, typically completing in under a minute.
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.
Plan and manage database infrastructure — This question tests Plan and manage database infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use Database Migration Service (DMS) with continuous replication — Database Migration Service (DMS) with continuous replication is the correct strategy because it uses change data capture (CDC) to replicate ongoing transactions from the source PostgreSQL database to Cloud SQL with minimal lag. This allows the application to remain fully operational during the migration, and the cutover can be performed in seconds by stopping writes to the source and promoting the target, achieving near-zero downtime.
What should I do if I get this PCDE 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.
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 →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating their on-premises PostgreSQL database to Cloud SQL. They want to minimize downtime during the migration. Which approach should they use?
easy
✓ A.Use Database Migration Service with continuous replication
B.Use pg_dump and pg_restore
C.Export data to CSV and import into Cloud SQL
D.Use a third-party ETL tool
Why A: Database Migration Service (DMS) with continuous replication is the correct approach because it uses change data capture (CDC) to replicate ongoing transactions from the source PostgreSQL database to Cloud SQL, enabling a near-zero downtime migration. DMS handles schema conversion, data validation, and automated failover, which minimizes the cutover window to seconds or minutes.
Variation 2. A company is migrating their on-premises PostgreSQL database to Cloud SQL. They want to minimize downtime during the migration. Which approach should they use?
easy
A.Export the database using pg_dump and import using psql in a single connection.
B.Use a VPN tunnel and set up Cloud SQL as a read replica of the on-premises primary.
✓ C.Use Database Migration Service (DMS) with continuous replication from an on-premises replica.
D.Use Database Migration Service (DMS) with a one-time full dump and import.
Why C: Database Migration Service (DMS) with continuous replication minimizes downtime by performing an initial full load of the database and then continuously replicating changes from the on-premises source to Cloud SQL. This allows the target to stay nearly synchronized with the source, so the final cutover can be completed in seconds or minutes rather than hours.
Last reviewed: Jun 25, 2026
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