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Difficulty: HardHigh Availability and Disaster Recovery Design

A global pharmaceutical corporation is designing a new cloud-based Manufacturing Execution System (MES) to monitor cleanroom environments and record regulatory batch records. The application will be deployed across two AWS Regions: eu-west-1 (Primary) and us-east-1 (Secondary). The system has a strict Recovery Time Objective (RTO) of 10 minutes and a Recovery Point Objective (RPO) of 1 minute.

The backend database is Amazon Aurora PostgreSQL. The application tier runs on Amazon EC2 instances in an Auto Scaling Group behind an Application Load Balancer (ALB) in each Region. The application instances must query a Private Hosted Zone (PHZ) in a shared services VPC for centralized configuration parameters. The application also requires highly available outbound internet connectivity in each Region to download regulatory compliance templates without being susceptible to a single Availability Zone (AZ) failure.

Which combination of actions should the Solutions Architect take to meet these requirements while minimizing downtime and maximizing fault tolerance? (Select TWO.)

  1. Deploy an Amazon Aurora Global Database with the primary cluster in eu-west-1 and a secondary cluster in us-east-1. Associate the Private Hosted Zone containing configuration details with the application VPCs in both AWS Regions.Answer
  2. Deploy a NAT Gateway in each Availability Zone in each Region's VPC, and configure the route tables of the private subnets in each Availability Zone to route outbound internet traffic through the NAT Gateway in their respective zone.Answer
  3. C
    To minimize database replication costs, establish a cross-region replication strategy using daily database snapshots copied to us-east-1, and use AWS Backup to restore the database cluster in the secondary Region during a failover event.
  4. D
    Deploy a single NAT Gateway in the first Availability Zone of each Region's VPC, and configure the route tables of the private subnets across all Availability Zones in that Region to route outbound internet traffic through this single NAT Gateway.
  5. E
    Associate the Private Hosted Zone with the shared services VPC in the primary Region, and rely on cross-region VPC peering to automatically resolve the configuration hostnames from the application VPC in the secondary Region.
  6. F
    Configure an Amazon Aurora Auto Scaling policy on the secondary cluster in us-east-1 to dynamically scale read replicas to handle write operations when the primary database cluster in eu-west-1 fails.

Answer

Deploy an Amazon Aurora Global Database with the primary cluster in eu-west-1 and a secondary cluster in us-east-1, associate the Private Hosted Zone containing configuration details with the application VPCs in both AWS Regions, and deploy a NAT Gateway in each Availability Zone in each Region's VPC with local routing in private subnets.
The solution requires deploying an Amazon Aurora Global Database to achieve the RPO of 1 minute, as it uses storage-based replication with latency of less than 1 second. Promoting the secondary cluster in the event of an outage takes less than 1 minute, matching the 10-minute RTO. Additionally, the Private Hosted Zone must be associated with the application VPCs in both Regions to resolve DNS hostnames locally. Outbound NAT Gateway redundancy is achieved by deploying a NAT Gateway in each Availability Zone, preventing an outage in one Availability Zone from interrupting outbound traffic from other Availability Zones.

Step-by-Step Solution

1
Evaluate database replication options against RTO (10 minutes) and RPO (1 minute) constraints.
Identify that Amazon Aurora Global Database provides sub-second replication (RPO) and quick cross-region promotion (RTO), whereas snapshot restore methods fail both metrics.
Ensures the selected database architecture satisfies the strict disaster recovery SLA.
2
Determine Private Hosted Zone (PHZ) association requirements for multi-region DNS resolution.
Determine that the PHZ must be explicitly associated with the VPCs in both regions, as cross-VPC DNS resolution does not automatically work over peered VPCs without association.
Enables instances in the secondary region to resolve configuration endpoints.
3
Assess NAT Gateway deployment strategy for Availability Zone fault tolerance.
Choose to deploy a NAT Gateway per Availability Zone rather than a single NAT Gateway shared across multiple zones.
Eliminates a single point of failure for outbound internet traffic in case of an Availability Zone outage.

Key Concept

Designing multi-region disaster recovery using Amazon Aurora Global Databases, private DNS routing configuration, and AZ-redundant internet gateways.
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Topics

High Availability and Disaster Recovery Design

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