Google PCA Design and plan a cloud solution architecture Practice Question
A company is migrating an on-premises PostgreSQL database to Cloud SQL with minimal downtime. The database is 1 TB and the network link has 500 Mbps bandwidth. Which migration approach is most appropriate?
⚠ Common exam trap
Google Cloud often tests the misconception that a simple dump-and-import (Option C) is acceptable for large databases, but the trap here is ignoring the 'minimal downtime' requirement, which demands a continuous replication solution like DMS rather than a batch export/import.
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 Database Migration Service to perform continuous replication and then promote Cloud SQL.
Database Migration Service (DMS) supports continuous replication from on-premises PostgreSQL to Cloud SQL using native PostgreSQL logical replication (pglogical or native publication/slot). This allows near-zero downtime by keeping the target in sync until promotion, which is ideal for a 1 TB database over a 500 Mbps link where a full dump/restore would take hours.
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 a Compute Engine instance with PostgreSQL replication and switch over.
Why it's wrong here
Setting up a Compute Engine instance with PostgreSQL replication requires the initial 1 TB dataset to be fully synchronised over the 500 Mbps link before replication can begin, which would take over four hours and exceed the minimal-downtime requirement. This approach is tempting because it mirrors a standard logical-replication strategy that works well for smaller databases or faster networks, where the initial sync completes within a brief maintenance window.
- ✗
Use BigQuery Data Transfer Service to replicate data.
Why it's wrong here
BigQuery Data Transfer Service loads data into BigQuery for analytics; it does not replicate into Cloud SQL, so the target database would never receive the data. It tempts because it is a managed transfer service, but it is correct for BigQuery ingestion, not Cloud SQL migration.
- ✗
Export the database as a SQL dump, transfer it to Cloud Storage, and import into Cloud SQL.
Why it's wrong here
A dump-and-import requires stopping writes for the entire export, transfer and import, so downtime scales with the 1 TB size over the 500 Mbps link. It tempts as the simplest manual method, and suits small databases where an outage window is acceptable.
- ✓
Use Database Migration Service to perform continuous replication and then promote Cloud SQL.
Why this is correct
Database Migration Service performs continuous replication from the on-premises PostgreSQL instance to Cloud SQL, keeping changes synchronised over the 500 Mbps link. Promoting Cloud SQL after replication catches up minimises downtime, unlike a one-off dump and load of 1 TB.
Go deeper
Related to this question
Learn chapter
Data Migration and Transfer Services
Key term
Service
A service is a software component or system that performs a specific function and is available to be used by other programs or users over a network.
Key term
Cloud SQL
Cloud SQL is a fully managed relational database service that lets you set up, maintain, and scale SQL databases (like MySQL, PostgreSQL, and SQL Server) in the cloud without managing the underlying infrastructure.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCA 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 PCA exam.