PCDE Practice Question: Manage a solution that can span multiple database technologies
You need to create a read replica of a Cloud SQL for PostgreSQL instance in a different region for disaster recovery. What must be true about the primary instance to support cross-region replicas?
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
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The primary instance must have automated backups enabled.
Cross-region read replicas for Cloud SQL for PostgreSQL require automated backups to be enabled on the primary instance. Automated backups are necessary to maintain the WAL (Write-Ahead Log) archive, which is used for replication. The primary does not need to be regional; a zonal (non-HA) instance can also support cross-region replicas. Point-in-time recovery is automatically enabled when automated backups are on, and the flag 'cloudsql.logical_decoding' must be set to 'on' (not 'off') for PostgreSQL replication.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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The primary instance must have point-in-time recovery disabled.
Why it's wrong here
Incorrect. Point-in-time recovery (PITR) relies on automated backups. Cross-region replicas require automated backups, which enable PITR. Disabling PITR would not prevent cross-region replicas, but it is not a requirement.
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The primary instance must be using a regional (high-availability) configuration.
Why it's wrong here
Incorrect. The primary instance does not need to be regional (HA). A zonal (non-HA) instance can also be used for cross-region replicas. High availability is not a prerequisite.
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The primary instance must have the 'cloudsql.logical_decoding' flag set to 'off'.
Why it's wrong here
Incorrect. For PostgreSQL, the 'cloudsql.logical_decoding' flag must be set to 'on' to enable replication. Setting it to 'off' would prevent cross-region replica creation.
- ✓
The primary instance must have automated backups enabled.
Why this is correct
Correct. Automated backups must be enabled on the primary instance because they provide the WAL archive needed for replication, including for cross-region replicas.
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