You run a multi-tier web app on EC2 instances behind an ALB in a primary Region. The ALB and Auto Scaling group are replicated in a backup Region, but the Auto Scaling group min and max are both set to zero. An RDS Multi-AZ instance stores data and has a read replica in the backup Region. Route 53 provides the user endpoint. You need to reduce RTO to under 15 minutes and enable automatic failover to the backup Region without an active-active strategy. What should you recommend?

The correct option achieves an RTO under 15 minutes with automatic failover by using Route 53 failover routing, which is designed for this scenario. A Route 53 health check monitors the primary application and, upon failure, automatically directs traffic to the backup ALB. An SNS notification triggered by the health check failure invokes a Lambda function in the backup Region. This Lambda promotes the RDS read replica to a standalone instance and scales up the Auto Scaling group from zero, preparing the backup environment to serve traffic. The first incorrect option uses latency-based routing, which is not suitable for automatic failover. The third incorrect option suggests an active-active setup (same min/max in both ASGs) and a complex, less efficient replication strategy for RDS, contradicting the requirement for an active-passive setup and fast RTO. The fourth incorrect option uses Global Accelerator with equal weights, which is also an active-active setup, not an active-passive failover strategy.