SAA-C03 Q539 · DR

Question

A company has a three-tier web application. An Application Load Balancer (ALB) is in front of Amazon EC2 instances that are in the ALB target group. An Amazon S3 bucket stores documents. The company requires the application to meet a recovery time objective (RTO) of 60 seconds. Which solution will meet this requirement?

Accepted Answer

**Option D** meets every requirement for a 60-second RTO:

1. **S3 Cross-Region Replication (CRR):** S3 objects are continuously replicated to a second Region, so documents are already available — no restore delay.

2. **Pre-provisioned and RUNNING EC2 instances:** A minimum set of EC2 instances is already running in the second Region behind a second ALB. This is the critical difference — because the instances are already running, there is no boot time, no AMI launch delay, and no configuration time. The application is warm and ready to serve traffic.

3. **Route 53 health-check-based failover:** Route 53 continuously monitors the health of the primary ALB. When health checks fail, Route 53 automatically updates DNS to point to the secondary ALB. With TTL settings and health check interval

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