AWS Certified Solutions Architect – Associate (SAA-C03)Design Resilient ArchitecturesHard
A global company needs to implement a disaster recovery (DR) strategy for its critical application, which runs on Amazon EC2 instances and an Amazon RDS for PostgreSQL database. The RTO for the application is 4 hours, and the RPO is 1 hour. They want a cost-effective solution that minimizes resources running in the DR region when not in use. Which DR strategy should they adopt?
- ABackup and Restore
- BWarm Standby
- CMulti-site Active/Active
- DPilot Light
Show answer & explanationAnswer & explanation
Correct answer: D. Pilot Light
The Pilot Light disaster recovery strategy involves keeping a minimal set of core resources provisioned in the DR region, like the database (RDS replica) and possibly pre-configured AMIs, while other resources are provisioned only during a disaster. This meets the RTO/RPO requirements of 4 hours/1 hour and is cost-effective by minimizing idle resources.
Why the other options are wrong
- A. Backup and Restore typically has a higher RTO (often 24+ hours) than 4 hours, as it involves restoring data and provisioning all infrastructure from scratch.
- B. Warm Standby involves a fully functional, scaled-down version of the application running in the DR region, which is more expensive than Pilot Light and might offer a lower RTO than needed.
- C. Multi-site Active/Active (Hot Standby) runs a full-scale application in both regions simultaneously, offering the lowest RTO/RPO (minutes/seconds) but is the most expensive, not fitting the 'cost-effective' criterion for the given RTO/RPO.
Pilot Light DR Strategy
A disaster recovery strategy where core infrastructure (e.g., database) is continuously running in the DR region, while other components are launched only during a disaster, balancing RTO/RPO with cost.
- A minimal version of the application's core is always running.
- Other resources are provisioned on demand during a disaster.
- Offers RTO in hours and RPO in minutes, balancing cost and recovery.
Memory trick: Pilot Light, a small glow, for DR, a cost-effective flow.