You are tasked with designing a disaster recovery strategy for an application running on GCP. The application uses Cloud Spanner, Cloud Pub/Sub, and App Engine. What should be your primary focus to ensure minimal downtime in case of a regional failure?

*Explanation:* To ensure minimal downtime in the event of a regional failure, the primary focus should be on implementing multi-region configurations for all services. This approach allows the application to automatically failover to another region if one becomes unavailable. Regular backups, although important, introduce recovery delays and may not provide immediate failover capabilities. Cloud Endpoints, Stackdriver Monitoring, and data replication across zones do not directly address the disaster recovery requirements.