Question 891 of 1,446
PCDE Practice Question: Manage a solution that can span multiple database technologies
A company is migrating its on-premises PostgreSQL database to Cloud SQL. The database is 2 TB and the migration must have minimal downtime. The source database supports continuous archiving. Which three steps should they take? (Choose THREE.)
⚠ Common exam trap
A common trap is confusing PostgreSQL's WAL-based replication with MySQL's binary logging; candidates familiar with MySQL may incorrectly select Option C, but for PostgreSQL to Cloud SQL, the correct approach uses Database Migration Service with continuous migration and WAL replication.
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
✓
Perform the cutover by promoting the Cloud SQL instance to primary.
Promoting the Cloud SQL instance to primary is the final step in a migration using continuous replication, which minimizes downtime by allowing the source database to remain operational until the cutover. This approach leverages Cloud SQL's ability to act as a replica that stays synchronized with the on-premises database via continuous archiving, ensuring data consistency with minimal interruption.
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 pg_dump to export the database and import into Cloud SQL.
Why it's wrong here
This would cause significant downtime.
- ✓
Perform the cutover by promoting the Cloud SQL instance to primary.
Why this is correct
Once replication is caught up, promote the Cloud SQL instance to become the new primary.
- ✗
Enable binary logging on the source database.
Why it's wrong here
Enabling binary logging is incorrect because PostgreSQL databases utilise Write-Ahead Logging (WAL) for replication and continuous archiving, not binary logs. The question explicitly states a PostgreSQL source, making this step technically invalid for the database type. This option is tempting as binary logging is essential for setting up replication and achieving minimal downtime during migrations from MySQL databases, such as to Cloud SQL for MySQL, where it serves a similar purpose to WAL in PostgreSQL.
- ✓
Set up Cloud SQL as an external replica of the on-premises database.
Why this is correct
Cloud SQL can be configured as a replica using logical replication.
- ✓
Use Database Migration Service with continuous migration.
Why this is correct
DMS supports continuous replication from PostgreSQL to Cloud SQL.
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Same concept, more angles
2 more ways this is tested on PCDE
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.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.
Variation 2. A company is migrating a large on-premises MySQL database to Cloud SQL. The source database supports heavy reporting queries that scan millions of rows and join multiple tables. The team wants to minimize downtime and avoid performance degradation during migration. Which migration approach should they use?
hard- A.Use gcloud sql import command to import a CSV export while the source database remains in use
- B.Create a BigQuery transfer service to move data from MySQL to Cloud SQL
- ✓ C.Set up Database Migration Service (DMS) with continuous replication from the source to Cloud SQL, then cut over when replication lag is minimal
- D.Use mysqldump to export the data and import it into Cloud SQL during a maintenance window
Why C: Database Migration Service (DMS) with continuous replication allows near-zero downtime migration by replicating changes from the source to Cloud SQL while the source remains operational. Export/import methods typically require downtime. Replicating to BigQuery is not relevant for Cloud SQL migration. Just changing instance size does not handle data migration.
Last reviewed: Jul 4, 2026
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