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Difficulty: MediumEnhancing Reliability and Disaster Recovery

An enterprise operates a critical inventory management application in the `us-east-1` Region. The application runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer (ALB). The database tier uses an Amazon RDS for PostgreSQL DB instance. The company wants to improve the reliability and disaster recovery posture of this workload by implementing a cross-Region solution in `us-west-2`. The solution must support a Recovery Time Objective (RTO) of 1515 minutes and a Recovery Point Objective (RPO) of 55 minutes. Which combination of actions should the solutions architect perform to meet these requirements? (Select TWO.)

  1. Create an Amazon RDS cross-Region read replica of the PostgreSQL DB instance in `us-west-2`. Configure the disaster recovery environment's Auto Scaling group with a minimum capacity of 11 instance to serve as a warm standby, and promote the replica during a failover event.Answer
  2. Configure Amazon Route 53 active-passive failover routing. Create a primary failover alias record pointing to the Application Load Balancer in `us-east-1` and associate it with a Route 53 health check. Create a secondary failover alias record pointing to the Application Load Balancer in `us-west-2`.Answer
  3. C
    Configure AWS Backup to take snapshots of the PostgreSQL database every 44 hours, copy the snapshots to `us-west-2`, and restore the database to a new instance during a failover event.
  4. D
    Configure Amazon Route 53 active-passive failover routing by creating a primary failover alias record pointing to the `us-east-1` Application Load Balancer and a secondary failover alias record pointing to the `us-west-2` Application Load Balancer, without associating health checks.
  5. E
    Configure outbound internet routing for the application servers in the `us-west-2` private subnets across 33 Availability Zones by routing all traffic through a single NAT Gateway deployed in one public subnet.

Answer

The solutions architect should create an Amazon RDS cross-Region read replica of the PostgreSQL database in the standby region and configure the Auto Scaling group with a minimum capacity of one instance. Additionally, they should configure Route 53 active-passive failover routing with a health check associated with the primary record.
To meet the 55-minute RPO, a cross-Region read replica is required because database updates are asynchronously replicated with very low latency. To meet the 1515-minute RTO, Route 53 active-passive failover routing with a health check must be configured on the primary record to detect failures and automatically point DNS queries to the standby region's load balancer. Additionally, the standby Auto Scaling group must have a minimum capacity of at least one instance to quickly handle the initial wave of traffic and scale up.

Step-by-Step Solution

1
Evaluate database replication options against the target RPO constraint.
Amazon RDS cross-Region read replicas offer continuous asynchronous replication, satisfying the RPO of 55 minutes. Snapshot restores scheduled every 44 hours violate the RPO.
Choosing the correct database replication method ensures data loss limits are maintained within the required recovery window.
2
Evaluate DNS failover routing mechanisms against the target RTO constraint.
Amazon Route 53 active-passive failover routing automatically shifts traffic within minutes, meeting the 1515-minute RTO. A health check must be associated with the primary record for automatic failover to function.
Without a health check on the primary record, Route 53 cannot determine when the endpoint is down, preventing automatic routing to the secondary region.
3
Ensure the backup region's internal networking supports high availability.
Avoid non-redundant NAT Gateways in the target region. Instead, deploy redundant NAT Gateways across Availability Zones to avoid a single point of failure.
Disaster recovery designs must ensure the standby site is highly available to successfully take over operations during an outage.

Key Concept

Disaster recovery designs must align database replication and DNS failover health checking to meet business RTO and RPO objectives without introducing infrastructure single points of failure.
Estimated Time:2m 0s
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Topics

Enhancing Reliability and Disaster Recovery