A global investment firm has recently deployed web servers in multiple AWS regions. Applications on these servers are critical to the firm. Only a few minutes of downtime is acceptable in the event of a disaster. Management is looking for a strategy that would provide faster RTO & low RPO with a constrained budget.
Which of the most appropriate disaster recovery strategies can be adopted?

Answer options:

A.Multi-Site
B.Pilot Light
C.Warm Standby
D.Backup & Restore

Correct Answer: C
RTO (Recovery Time Objective) is a period for which downtime is observed post-disaster. RPO is a recovery point objective that defines the amount of data loss when there is a disaster. With the Warm-Standby disaster recovery strategy, all resources deployed at primary sites are deployed at secondary sites at a minimum size. In case of disaster at the primary site, resources at the secondary site are scaled up to achieve load as that of the primary site. This strategy provides a faster RTO & low RPO. When the primary site is up & running, resources at the secondary site are not running at full load which lowers cost. It costs lower than that of Multi-site strategy in which both primary & secondary sites are running with resources at full load. 
Option A is incorrect as Multi-site will provide zero downtime during a disaster when full production scale resources are running at the secondary sites. But this will incur high costs. Since the firm is looking for disaster recovery with a limited budget, this is not the correct option.
Option B is incorrect as the Pilot light strategy will provide RTO in tens of minutes. RPO will be higher as resources will be initiated only once a disaster occurs at the primary site. 
Option D is incorrect as the Backup & restore strategy will provide RTO in hours & will incur higher RPO.
For more information on disaster recovery strategies, refer to the following URL,
https://docs.aws.amazon.com/whitepapers/latest/disaster-recovery-workloads-on-aws/disaster-recovery-workloads-on-aws.pdf