Question

Difficulty: HardHigh Availability and Disaster Recovery Design

A financial technology company is designing a disaster recovery (DR) architecture for a critical transaction ledger application. The application will be deployed across two AWS Regions: `us-east-1` as the primary region and `us-west-2` as the secondary region. The company has specified a Recovery Time Objective (RTO) of 1515 minutes and a Recovery Point Objective (RPO) of 22 minutes. The application runs on Amazon EC2 instances in Auto Scaling groups behind Application Load Balancers, and uses an Amazon Aurora PostgreSQL DB cluster. The DR strategy must minimize running costs during normal operations while meeting the RTO and RPO, and public traffic must automatically fail over to the secondary region if the primary region becomes unhealthy. Which combination of actions should the Solutions Architect select to meet these requirements? (Select TWO.)

  1. Create an Amazon Aurora Global Database with the primary cluster in `us-east-1` and a secondary cluster in `us-west-2`. Deploy a minimum-size Aurora replica instance in the secondary cluster to minimize running cost, and use automation to scale up the instance class before promoting the secondary cluster during a failover event.Answer
  2. Configure Amazon Route 53 public DNS with active-passive failover routing. Point the primary record to the Application Load Balancer in `us-east-1` with an associated Amazon Route 53 health check, and point the secondary record to the Application Load Balancer in `us-west-2`.Answer
  3. C
    Configure AWS Backup to take hourly snapshots of the Aurora DB cluster in `us-east-1` and copy them to `us-west-2`. In the event of a disaster, restore the DB cluster from the latest snapshot in the secondary region and update the application configuration.
  4. D
    Set up an Amazon Aurora PostgreSQL DB cluster with cross-region read replicas. Enable Aurora Auto Scaling on the reader instances in `us-west-2` to handle write traffic by automatically promoting the reader with the lowest replication lag.
  5. E
    Configure Route 53 with latency-based routing to split traffic between the Application Load Balancers in both regions, and create a single Route 53 Private Hosted Zone associated only with the `us-east-1` VPC for internal microservice resolution.

Answer

Create an Amazon Aurora Global Database with a scaled-down secondary instance and configure Route 53 active-passive failover routing.
The correct strategy combines Aurora Global Database with a scaled-down secondary instance and Route 53 active-passive failover routing. Aurora Global Database replication has a lag of less than 11 second, which easily meets the 22-minute RPO. Using a smaller instance in the secondary cluster minimizes active costs, and scaling it up during failover can be completed well within the 1515-minute RTO. Route 53 failover routing with health checks ensures that public traffic is dynamically redirected to the secondary load balancer when the primary region is down.

Step-by-Step Solution

1
Evaluate database replication options against the RPO constraint.
Amazon Aurora Global Database is chosen because its physical replication lag is typically less than 11 second, easily satisfying the 22-minute RPO constraint, whereas snapshot-based approaches yield up to 6060 minutes of data loss.
Choosing the correct database replication method ensures data recovery aligns with business requirements.
2
Optimize database cost for the secondary region while keeping within the RTO limit.
A smaller database instance class is deployed in the secondary region to minimize costs, and an automation script is prepared to scale it up to match the primary instance size before promotion during failover. This process takes under 1010 minutes, fitting inside the 1515-minute RTO.
This maintains a cost-effective warm standby posture while preserving the ability to scale to production capacity.
3
Configure DNS routing for automated failover.
Route 53 active-passive failover routing is configured with health checks targeting the Application Load Balancer in the primary region. Traffic is redirected to the secondary region automatically when the health check fails.
This establishes automatic redirection of client traffic during an outage without manual DNS record updates.

Key Concept

Disaster recovery design involves trade-offs between cost, RTO, and RPO. Aurora Global Database provides near-zero replication lag for low RPOs, while Route 53 active-passive failover routing ensures automated application traffic redirection.
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