Google ACE Deploying and Implementing a Cloud Solution Practice Question
A company wants to migrate an on-premises MySQL database to Cloud SQL with minimal downtime. The database is 500 GB. Which TWO steps should be taken? (Choose 2 correct answers.)
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
✓
Create a Cloud SQL instance to serve as the target for the migration.
To minimize downtime, you can perform a Database Migration Service (DMS) continuous migration or export/import with a consistent snapshot. DMS supports MySQL and provides continuous sync. Alternatively, you can export the database using mysqldump, then import, but this requires downtime. However, for minimal downtime, DMS is best. Another approach is to create a read replica then promote, but Cloud SQL does not support external read replicas directly. The correct two are: use DMS for continuous migration, and optionally create a clone for testing, but the question asks for migration steps. The best two from the options: use DMS migration job and create a Cloud SQL instance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Create a Cloud SQL instance to serve as the target for the migration.
Why this is correct
The Database Migration Service requires a pre-provisioned Cloud SQL instance as the destination, so creating one first defines the target tier, storage, and network configuration before any migration job is started. Without an existing instance, DMS has nowhere to replicate the initial snapshot or stream incoming changes. This is the necessary first step in a low-downtime migration, even though the actual data movement happens later via a DMS job.
- ✗
Export the database using gcloud sql export sql, then import to Cloud SQL.
Why it's wrong here
Using gcloud sql export sql to dump the source to Cloud Storage and then importing it into Cloud SQL is an offline, batch-oriented process that typically requires stopping writes or making the source read-only to guarantee a consistent snapshot. This forced downtime violates the minimal-downtime objective, and because the export is a one-time copy, any writes that occur after the dump are lost unless you also manually capture and replay binlog entries. It is only suitable for small databases with a scheduled maintenance window.
- ✗
Create a Cloud SQL instance and configure it as an external replica of the on-premises database.
Why it's wrong here
Cloud SQL does not support being configured as a replica of an external, on-premises MySQL instance; external replication is one-directional and only allows an external MySQL instance (or another Cloud SQL instance) to replicate from Cloud SQL as the source. The DMS service is the only Cloud-native way to bring on-premises changes into Cloud SQL, and even then it uses its own replication agents rather than the Cloud SQL instance acting as a replica. This option is therefore technically impossible and would not migrate any data.
- ✗
Use mysqldump to backup the database and restore into Cloud SQL.
Why it's wrong here
mysqldump produces a logical backup that must be manually restored into Cloud SQL, and during the dump the source database must be locked or taken offline to ensure the backup is consistent—directly contradicting a minimal-downtime requirement. For a large database, the dump and import process can take hours, and any changes committed after the dump are not captured unless you separately set up binlog replay. This approach is a one-time data migration, not a continuous sync, so it does not satisfy the need to keep the on-premises and cloud databases in sync until cutover.
- ✓
Use Database Migration Service to create a continuous migration job.
Why this is correct
Database Migration Service (DMS) is the correct service for a minimal-downtime migration because it performs an initial copy of the database and then uses MySQL binary log replication to continuously apply changes to the target Cloud SQL instance. This allows you to cut over with only a brief pause in writes, but it requires the target Cloud SQL instance to exist before the migration job is created. Therefore, while DMS is the overall correct approach, the first operational step must be creating that target instance.
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Related to this question
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Google Cloud Platform Overview
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.
Key term
Snapshot
A snapshot is a point-in-time copy of a system's data or state, used for backup, recovery, or testing without disrupting the original.
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Written by Johnson Ajibi, MSc IT Security
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