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Difficulty: Very hardEnhancing Reliability and Disaster Recovery

An enterprise hosts a critical transaction session synchronization layer across two AWS Regions. The compute layer runs on Amazon Elastic Container Service (Amazon ECS) on AWS Fargate in a Production Account. The caching and session state layer is managed by an Amazon ElastiCache for Redis Global Datastore, with the primary cluster in us-east-1 and a read-only secondary cluster in us-west-2. Internal microservices resolve the Redis cluster endpoint using a Route 53 Private Hosted Zone (PHZ) for cache.internal managed in a separate Shared Services Account. The enterprise wants to optimize their disaster recovery (DR) strategy to achieve a Recovery Time Objective (RTO) of under 10 minutes and a Recovery Point Objective (RPO) of under 1 minute. During a DR simulation where a primary region outage is simulated, the secondary ECS tasks in us-west-2 fail to resolve cache.internal, and write operations to the cache in us-west-2 are blocked because the secondary cluster remains read-only. Which TWO actions should the Solutions Architect take to resolve these issues and establish a reliable multi-region DR failover process?

  1. In the Shared Services Account, create a VPC association authorization for the Production Account's us-west-2 VPCs. In the Production Account, associate the Route 53 Private Hosted Zone with the us-west-2 VPCs using the AWS CLI or SDK.Answer
  2. Implement AWS Route 53 Application Recovery Controller (ARC) routing controls to manage regional traffic failover, and create a failover automation script that promotes the secondary ElastiCache cluster in us-west-2 to primary.Answer
  3. C
    Use AWS Resource Access Manager (RAM) to share the Route 53 Private Hosted Zone from the Shared Services Account to the Production Account, allowing the us-west-2 VPCs to inherit the DNS resolution rules.
  4. D
    Configure Route 53 failover routing policies using health checks targeting the Redis cluster endpoints to automatically promote the secondary cluster to primary when the primary cluster becomes unhealthy.
  5. E
    Enable multi-region multi-writer replication on the ElastiCache Global Datastore to allow concurrent writes in both regions, and use Route 53 latency-based routing to automatically direct write traffic.

Answer

Create a VPC association authorization in the Shared Services Account and associate the private hosted zone with the us-west-2 VPCs in the Production Account; and implement AWS Route 53 ARC routing controls to manage failover and execute an API script to promote the secondary ElastiCache cluster.
The correct options resolve the two major issues. First, establishing cross-account DNS resolution requires creating a VPC association authorization in the hosted zone's account (Shared Services) and then performing the association in the VPC's account (Production). Second, ElastiCache for Redis Global Datastore does not automate cross-region write promotion; the secondary cluster must be promoted to primary via an API call (using AWS SDK/CLI) during a failover event. Route 53 Application Recovery Controller (ARC) routing controls manage regional traffic redirection reliably without relying on unstable DNS health checks that might trigger split-brain states.

Step-by-Step Solution

1
Create a VPC association authorization from the owner account.
The Shared Services Account authorizes the association between the Private Hosted Zone and the us-west-2 VPC in the Production Account.
Route 53 requires explicit cross-account permission before a private hosted zone can be associated with a VPC in a different AWS account.
2
Associate the VPC with the Private Hosted Zone.
The Production Account associates its us-west-2 VPC with the hosted zone.
Allows ECS tasks in the secondary region to resolve local resources using the private hosted zone name.
3
Implement Route 53 Application Recovery Controller (ARC) routing controls.
Defines routing control states that can be toggled to shift regional ingress traffic systematically.
Provides deterministic control over traffic routing to prevent premature or split-brain failovers.
4
Orchestrate ElastiCache secondary cluster promotion.
Promotes the us-west-2 secondary cluster to primary via API/script.
ElastiCache Global Datastore requires manual or scripted promotion because it does not perform automatic failover of the primary write endpoint across regions.

Key Concept

Cross-account private DNS configuration and automated database promotion strategies for multi-region disaster recovery.
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Topics

Enhancing Reliability and Disaster Recovery