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Difficulty: EasyHigh Availability and Disaster Recovery Design

A company is designing a disaster recovery (DR) architecture for a web application. The business requirements specify a Recovery Time Objective (RTO) of 1515 minutes and a Recovery Point Objective (RPO) of 55 minutes. The solutions architect needs to minimize ongoing running costs and infrastructure complexity.

Which disaster recovery strategy should the solutions architect select to meet these requirements?

  1. A Pilot Light strategy that replicates the database to the secondary region using Amazon Aurora Global Database, and maintains stopped application servers in the secondary region that are started during a failover event.Answer
  2. B
    A Backup and Restore strategy that performs daily database backups to Amazon S3 in the secondary region, and restores all resources during a disaster.
  3. C
    A Pilot Light strategy that uses Amazon Aurora Global Database for replication, but associates the Route 53 Private Hosted Zone for database endpoint resolution only with the primary region's VPC.
  4. D
    A Warm Standby strategy that uses an Amazon RDS Multi-AZ deployment across regions, and configures the standby database instance in the secondary region to serve active read traffic.

Answer

The Pilot Light strategy that replicates the database using Amazon Aurora Global Database and maintains stopped application servers in the secondary region to be started during failover.
The Pilot Light strategy using Amazon Aurora Global Database is correct. Aurora Global Database handles database replication asynchronously with sub-second lag, ensuring the 55-minute RPO is met. Keeping the application servers stopped under normal operations minimizes ongoing compute costs, and starting them during a failover event can be completed well within the 1515-minute RTO.

Step-by-Step Solution

1
Evaluate the RPO requirement against the candidate replication strategies.
The target RPO is 55 minutes. Amazon Aurora Global Database provides sub-second replication lag, meeting this requirement, whereas daily database backups fail to meet it.
Choosing a replication strategy with lag lower than the target RPO is necessary to prevent data loss beyond the business limit.
2
Evaluate the RTO and cost requirements against the application tier status.
A Pilot Light strategy meets the 1515-minute RTO by keeping the database active in the DR region while avoiding the costs of running active application servers by keeping them stopped until failover.
Maintaining stopped resources or infrastructure templates minimizes active running costs while ensuring they can be provisioned within the target RTO.
3
Verify DNS and cross-region connectivity requirements for the database.
The Route 53 Private Hosted Zone used for database resolution must be associated with the secondary VPC to ensure the failover application servers can connect to the database.
Failing to link the hosted zone to the secondary VPC prevents resolution of internal database endpoints during a disaster recovery event.

Key Concept

Disaster recovery strategy selection based on RTO, RPO, and cost constraints.
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Topics

High Availability and Disaster Recovery Design

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