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Difficulty: MediumEnhancing Reliability and Disaster Recovery

An e-commerce company hosts its transaction processing workload in the us-east-1 Region. The compute layer consists of Amazon ECS tasks running on AWS Fargate behind an Application Load Balancer (ALB). The data layer uses an Amazon Aurora PostgreSQL database. Currently, all outbound internet traffic from the private subnets is routed through a single NAT Gateway in one Availability Zone.

To enhance reliability and prepare for disaster recovery, the company wants to implement a multi-region strategy in the us-west-2 Region. The design must achieve a Recovery Time Objective (RTO) of less than 15 minutes and a Recovery Point Objective (RPO) of less than 5 minutes.

Which configuration represents the most reliable and cost-effective solution that meets these requirements?

  1. Convert the database to an Amazon Aurora Global Database with a secondary cluster in us-west-2. Deploy the ECS service in us-west-2 with the desired task count set to 1. In both Regions, provision a NAT Gateway in each Availability Zone. Use AWS Route 53 Application Recovery Controller (ARC) routing controls to manage failover between the Application Load Balancers in both Regions.Answer
  2. B
    Configure hourly AWS Backup snapshot replication from us-east-1 to us-west-2 for the Aurora database. Deploy the ECS service in us-west-2 with the desired task count set to 0. Maintain the single NAT Gateway in us-east-1 and deploy a single NAT Gateway in us-west-2. During an outage, restore the database from the latest snapshot and scale up the ECS tasks.
  3. C
    Convert the database to an Amazon Aurora Global Database with a secondary cluster in us-west-2. Deploy the ECS service in us-west-2 with the desired task count set to 1. Maintain a single NAT Gateway in each Region to route outbound traffic for the private subnets. Create Route 53 failover routing records pointing to the ALBs, but do not configure or associate Route 53 health checks to avoid false failovers.
  4. D
    Convert the database to an Amazon Aurora Global Database with a secondary cluster in us-west-2. Deploy the ECS service in us-west-2 with the desired task count set to 1. In both Regions, provision a NAT Gateway in each Availability Zone. Create Route 53 failover routing records pointing to the ALBs in both Regions, but configure the primary record's health check to monitor a static status page on Amazon S3 rather than the application endpoint.

Answer

Convert the database to an Amazon Aurora Global Database with a secondary cluster in us-west-2. Deploy the ECS service in us-west-2 with the desired task count set to 1. In both Regions, provision a NAT Gateway in each Availability Zone. Use AWS Route 53 Application Recovery Controller (ARC) routing controls to manage failover between the Application Load Balancers in both Regions.
The correct option addresses all the design constraints. An Amazon Aurora Global Database provides sub-second cross-region replication to us-west-2, satisfying the 5-minute RPO. Having the ECS service running with at least one task verifies deployment health and allows standard scaling policies to meet the 15-minute RTO. Redundant NAT Gateways ensure high availability within each region. AWS Route 53 ARC routing controls provide reliable, deterministic multi-region failover management.

Step-by-Step Solution

1
Select a replication strategy for the database layer that achieves an RPO of less than 5 minutes.
Amazon Aurora Global Database provides millisecond-level cross-region replication, easily satisfying the 5-minute RPO requirement.
Traditional backup restore methods (like hourly snapshots) have an RPO that is too high.
2
Ensure the compute layer can be restored within the 15-minute RTO.
ECS tasks can be scaled up quickly from a warm standby configuration (minimum 1 task) within minutes.
Running a minimal set of tasks verifies service health in the secondary region and allows fast auto-scaling during failover.
3
Eliminate single points of failure in the egress network path.
NAT Gateways are deployed in each Availability Zone in both regions.
A single NAT Gateway per region is a single point of failure that violates reliability best practices.
4
Implement a reliable cross-region failover mechanism.
AWS Route 53 Application Recovery Controller (ARC) is configured with routing controls to orchestrate failover.
Route 53 ARC routing controls allow deterministic and safe failover alignment across the data and application tiers.

Key Concept

Disaster recovery strategy selection (RTO/RPO), multi-AZ network redundancy, and automated multi-region failover.
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Topics

Enhancing Reliability and Disaster Recovery