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Difficulty: MediumEnhancing Reliability and Disaster Recovery

An enterprise runs a critical compliance application in the us-east-1 Region within a Production AWS account. The application tier consists of Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer. The database tier uses an Amazon RDS for PostgreSQL DB instance. The enterprise wants to set up a disaster recovery (DR) solution in the us-west-2 Region with a Recovery Time Objective (RTO) of 30 minutes and a Recovery Point Objective (RPO) of 15 minutes. Outbound internet traffic in both regions must go through a centralized Network AWS account via AWS Transit Gateway. Which configuration meets the recovery objectives at the lowest cost while ensuring a highly reliable architecture?

  1. Create an Amazon RDS for PostgreSQL cross-Region read replica in us-west-2. In the Network account, deploy redundant NAT Gateways across multiple Availability Zones in us-west-2 connected to the Transit Gateway. In the Production account, deploy a pilot light Auto Scaling group with a minimum capacity of 0 in us-west-2. During a failover event, use a script to promote the RDS replica to primary, scale up the Auto Scaling group, and update Route 53 DNS records.Answer
  2. B
    Configure AWS Backup in the Production account to take daily snapshots of the RDS DB instance and copy them to us-west-2. In the Network account, deploy redundant NAT Gateways across multiple Availability Zones in us-west-2. In the Production account, pre-deploy the application infrastructure in us-west-2. During a failover event, restore the database from the copied snapshot and update Route 53 DNS records.
  3. C
    Create an Amazon RDS for PostgreSQL cross-Region read replica in us-west-2. In the Network account, deploy a single NAT Gateway in a single Availability Zone in us-west-2 to handle outbound internet traffic for the standby VPC. In the Production account, deploy a pilot light Auto Scaling group with a minimum capacity of 0 in us-west-2. During a failover event, promote the RDS replica, scale up the Auto Scaling group, and update Route 53 DNS records.
  4. D
    Create an Amazon RDS for PostgreSQL cross-Region read replica in us-west-2. In the Network account, deploy redundant NAT Gateways across multiple Availability Zones in us-west-2. Configure Amazon Route 53 active-passive failover routing with health checks. Rely on Route 53 to automatically promote the RDS read replica in us-west-2 to primary and scale the application instances when the primary endpoint is unhealthy.

Answer

Create an Amazon RDS for PostgreSQL cross-Region read replica in us-west-2. In the Network account, deploy redundant NAT Gateways across multiple Availability Zones in us-west-2 connected to the Transit Gateway. In the Production account, deploy a pilot light Auto Scaling group with a minimum capacity of 0 in us-west-2. During a failover event, use a script to promote the RDS replica to primary, scale up the Auto Scaling group, and update Route 53 DNS records.
The correct configuration uses Amazon RDS cross-Region replication to meet the 15-minute RPO, a pilot light Auto Scaling group to minimize idle costs in the secondary region, and scripting to automate failover within the 30-minute RTO. Additionally, it ensures outbound network reliability by using redundant NAT Gateways across multiple Availability Zones in the Network account.

Step-by-Step Solution

1
Evaluate the RPO requirement of 15 minutes.
Determine that cross-Region read replication is required because daily backups have an RPO of 24 hours.
Asynchronous RDS cross-Region replication provides lag times typically under a few minutes, satisfying the 15-minute RPO.
2
Evaluate the RTO requirement of 30 minutes.
A pilot light deployment with automated scripting is selected to promote the database and scale instances.
Scripted promotion of the replica and scaling the Auto Scaling group from 0 can easily be completed within the 30-minute target.
3
Analyze outbound networking path reliability.
Redundant NAT Gateways must be deployed across multiple Availability Zones in the secondary Region.
A single NAT Gateway creates a single point of failure, violating the reliability requirements of the architecture.
4
Assess Route 53 automatic failover capabilities.
Identify that DNS routing changes are automatic, but database promotion and infrastructure scaling require custom automation.
Route 53 cannot perform application-level tasks like database promotion or Auto Scaling group modification.

Key Concept

Designing cost-effective, highly reliable multi-Region disaster recovery architectures utilizing pilot light patterns, RDS cross-Region replication, and redundant NAT Gateways.
Estimated Time:2m 0s
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Topics

Enhancing Reliability and Disaster Recovery