This answer is correct because it meets the requirements of having an optimal and highly available environment with automatic failover. According to the Google Cloud documentation1, a regional Cloud SQL instance is an instance that has a primary server in one zone and a standby server in another zone within the same region. The primary and standby servers are kept in sync using synchronous replication, which ensures zero data loss and minimal downtime in case of a zonal outage or an instance failure. If the primary server becomes unavailable, Cloud SQL automatically fails over to the standby server, which becomes the new primary server1.