GCP Professional Data Engineer Practice Question

Your team runs a nightly Dataflow ETL job that reads transactional data from a Cloud SQL for PostgreSQL instance and writes aggregates back into the same database. Last month a zonal outage in the instance's zone caused the job to fail and delayed reporting. You must harden the database against a single-zone failure while minimizing application changes and operational overhead. Which approach best meets the requirement?

Create a cross-region read replica and direct Dataflow to use the replica; Cloud SQL will automatically promote it and redirect traffic during a failure.
Provision a second single-zone Cloud SQL instance in a different zone, configure logical replication, and switch the job's connection string to this replica during an outage.
Export the database to Cloud Storage each night and have the Dataflow job read from the export if the primary instance is unavailable.
Convert the database to a Cloud SQL regional high-availability configuration so a synchronous standby in another zone can take over automatically while keeping the same private IP.

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Answer Description

A Cloud SQL high-availability (regional) configuration keeps a primary and a synchronous standby instance in different zones of the same region. If the primary zone becomes unavailable, Cloud SQL automatically promotes the standby, retains the same private IP address, and requires no changes to client connection strings or manual intervention-meeting the need for resiliency with minimal operational effort.

A cross-region read replica provides disaster-recovery for regional outages, but it is asynchronous, read-only, and requires manual promotion and connection updates. Exporting data to Cloud Storage does not protect the live database or support in-place writes. Building a second single-zone instance with logical replication would need manual failover and application reconfiguration, increasing operational burden.

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