A research institute runs an internal reporting application on EC2 with an Amazon RDS for MySQL database in a single Region. The workload is used during office hours only, leadership accepts a recovery time objective of up to several hours and a recovery point objective of up to a day for a Regional disaster, and the dominant constraint is keeping standby costs as close to zero as possible. Which disaster recovery strategy MOST cost-effectively satisfies these relaxed targets?
- AMaintain a cross-Region RDS read replica and a minimal scaled-down Auto Scaling group in the recovery Region at all times, promoting the replica and scaling out the fleet when the primary Region eventually fails.
- BRun a warm standby in the recovery Region with a reduced-capacity fleet and an RDS read replica continuously serving a fraction of live reporting traffic alongside the primary Region.
- CUse AWS Elastic Disaster Recovery to continuously replicate the EC2 and database servers at the block level into a staging area in the recovery Region for launch on demand during a disaster.
- DTake automated daily RDS snapshots and AMIs, copy them to the recovery Region on a daily schedule, and restore the database and launch the application from those copies after a Regional disaster. Correct
Why A is wrong: A pilot light keeps a replica running continuously, which costs more than necessary given the institute accepts a day of data loss and several hours of downtime, so it overspends for these relaxed targets.
Why B is wrong: Warm standby keeps compute and a replica running at all times, which far exceeds the near-zero standby cost the institute wants given it tolerates a day of data loss and hours of downtime.
Why C is wrong: Elastic Disaster Recovery gives a seconds-level RPO and minutes-level RTO, but the continuous replication and staging resources cost more than needed when a one-day RPO is acceptable.
Why D is correct: Backup and restore stores only inexpensive snapshots and images between events, matching a one-day RPO and a several-hour RTO, which makes it the cheapest strategy that still meets these relaxed objectives.