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Difficulty: EasyMulti-AZ, Multi-Region Architectures and Disaster Recovery (DR)

A company is designing a disaster recovery (DR) strategy for a database on AWS. The company requires a Recovery Point Objective (RPO) of 11 hour and a Recovery Time Objective (RTO) of 1515 minutes. The solutions architect wants to minimize ongoing running costs. Which of the following strategies meets these requirements at the lowest cost?

  1. A Pilot Light strategy that replicates the database data to the secondary AWS Region, runs a minimal database instance, and provisions the application servers from Amazon Machine Images (AMIs) during a failover.Answer
  2. B
    A Pilot Light strategy that keeps all application servers stopped in the secondary region, expecting them to process live traffic immediately with zero startup time upon DNS failover.
  3. C
    A database replication strategy that copies data to an Amazon RDS Read Replica in the secondary region, and configures the application to write directly to the Read Replica during a failover without promoting it.
  4. D
    A Backup and Restore strategy that stores database backups in Amazon S3 Glacier Flexible Retrieval, and uses standard retrieval to restore the database to a new instance within the 1515-minute failover window.

Answer

A Pilot Light strategy that replicates the database data to the secondary AWS Region, runs a minimal database instance, and provisions the application servers from Amazon Machine Images (AMIs) during a failover.
The correct strategy is a Pilot Light architecture. In this setup, critical data such as the database is replicated to the disaster recovery region and kept active, while application servers remain unprovisioned (or exist only as AMIs) to minimize ongoing costs. The application servers can be quickly provisioned from AMIs during failover, which satisfies the 1515-minute RTO.

Step-by-Step Solution

1
Analyze the RTO and RPO requirements.
The RPO is 11 hour (permits minimal data loss) and the RTO is 1515 minutes (demands fast recovery).
This determines which DR strategies are capable of meeting the recovery window.
2
Evaluate the cost constraint.
Backup and Restore is too slow for a 1515-minute RTO. Warm Standby and Multi-site are too expensive. Pilot Light is the most cost-effective strategy that can meet the RTO.
We must find the strategy that satisfies the recovery objectives at the lowest ongoing running cost.
3
Identify the correct implementation of the Pilot Light strategy.
Replicating data to an active database and keeping application servers unprovisioned until failover meets both the cost and RTO requirements.
This matches the definition of a Pilot Light strategy.

Key Concept

Disaster recovery strategies differ in cost and recovery times. Pilot Light maintains database replication with minimal resources and provisions the rest of the application stack only during failover, offering a balance of low cost and quick recovery.
Estimated Time:1m 0s
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Topics

Multi-AZ, Multi-Region Architectures and Disaster Recovery (DR)

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