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Difficulty: EasyHigh Availability and Disaster Recovery Design

A company is designing a disaster recovery (DR) architecture on AWS for a mission-critical web application. The application requires a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 5 minutes. The architecture must minimize ongoing standby infrastructure costs while still meeting the RTO and RPO. Which strategy should a solutions architect recommend to meet these requirements?

  1. Configure a Warm Standby DR pattern in a secondary AWS Region by running a scaled-down deployment of the application tier and continuously replicating the database tier. Use Route 53 Failover routing with health checks to redirect traffic to the secondary region during an outage, and scale up the application tier upon failover.Answer
  2. B
    Configure a Pilot Light DR pattern in a secondary AWS Region by replicating the database tier but keeping the application tier completely shut down. Use Route 53 Latency routing with health checks to automatically provision the application tier from Amazon Machine Images (AMIs) during a failover event.
  3. C
    Configure a Backup and Restore DR pattern using cross-region Amazon Aurora snapshots scheduled every 4 hours. Configure Route 53 Failover routing to direct users to a static website hosted in Amazon S3 until the database and application are fully restored in the secondary region.
  4. D
    Configure a Multi-Region Active-Active DR pattern by deploying identical, fully-scaled application tiers in both regions. Configure Route 53 Geolocation routing to distribute traffic, and use Amazon RDS Multi-AZ standby instances in the secondary region to serve read traffic during normal operations to offset standby costs.

Answer

Configure a Warm Standby DR pattern in a secondary AWS Region by running a scaled-down deployment of the application tier and continuously replicating the database tier. Use Route 53 Failover routing with health checks to redirect traffic to the secondary region during an outage, and scale up the application tier upon failover.
The Warm Standby disaster recovery strategy meets the RPO of 5 minutes by continuously replicating the database to a secondary region. It satisfies the 15-minute RTO by maintaining a pre-provisioned, scaled-down application tier that can quickly scale up under load. This approach minimizes ongoing costs compared to a fully-scaled Active-Active deployment, and utilizes Route 53 Failover routing to automate redirection when the primary region is degraded.

Step-by-Step Solution

1
Analyze the RPO requirement to determine database replication needs.
An RPO of 5 minutes necessitates real-time or continuous database replication. This rules out Backup and Restore strategies that rely on periodic snapshots.
Periodic backups cannot guarantee a maximum data loss window of 5 minutes.
2
Analyze the RTO requirement to determine application-tier readiness.
An RTO of 15 minutes requires application servers to be already running (even at a reduced scale) so they can handle traffic quickly. This rules out Pilot Light, which requires provisioning and bootstrapping instances from scratch.
Bootstrapping instances from AMIs during a failover event typically exceeds 15 minutes.
3
Evaluate the remaining options based on cost and architectural validity.
Warm Standby runs at a reduced scale, minimizing cost compared to Active-Active which runs fully-scaled environments. Additionally, RDS Multi-AZ replication cannot span across regions or serve read traffic, making the Active-Active option architecturally invalid.
Warm Standby is the most cost-effective valid strategy that meets all constraints.

Key Concept

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

High Availability and Disaster Recovery Design

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