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Difficulty: EasyMulti-AZ, Multi-Region Architectures and Disaster Recovery (DR)

A real estate listing platform hosts its application on AWS using Amazon EC2 instances and an Amazon RDS for PostgreSQL DB instance. The platform needs to establish a cost-effective disaster recovery (DR) plan in a secondary Region. The company specifies a Recovery Point Objective (RPO) of 2424 hours and a Recovery Time Objective (RTO) of 44 hours. The DR plan must minimize ongoing running costs. Which TWO configurations should a solutions architect recommend to meet these requirements at the lowest cost?

  1. Configure daily automated snapshots of the RDS DB instance and copy them to the destination Region.Answer
  2. Store an AWS CloudFormation template of the application tier in an Amazon S3 bucket in the destination Region to deploy resources on demand.Answer
  3. C
    Export the database backups directly to Amazon S3 Glacier Deep Archive daily to minimize storage costs.
  4. D
    Create a cross-region RDS Read Replica and use Amazon Route 53 latency routing to automatically redirect write traffic during a failover.
  5. E
    Deploy a Warm Standby environment in the destination Region with all EC2 instances running at full capacity to ensure zero startup time.

Answer

Configure daily automated snapshots of the RDS DB instance and copy them to the destination Region, and store an AWS CloudFormation template of the application tier in an Amazon S3 bucket in the destination Region to deploy resources on demand.
To meet an RPO of 2424 hours and an RTO of 44 hours at the lowest cost, a Backup and Restore strategy is the ideal solution. Configuring daily automated snapshots of the database and copying them to the destination Region meets the 2424-hour RPO. Storing an AWS CloudFormation template in Amazon S3 in the secondary Region allows you to deploy the application's compute resources on demand within the 44-hour window during a disaster, incurring no compute costs during normal operations.

Step-by-Step Solution

1
Analyze the RTO, RPO, and budget requirements.
The target requirements are RPO = 2424 hours, RTO = 44 hours, and the strategy must minimize ongoing costs.
An RPO of 2424 hours and an RTO of 44 hours allow for a Backup and Restore strategy, which is the most cost-effective disaster recovery strategy since no compute resources run actively in the backup Region.
2
Select the database replication strategy that meets the RPO at the lowest cost.
Choose daily database snapshots copied cross-region.
Creating daily snapshots fits the 2424-hour RPO, and copying them to the secondary Region incurs only standard storage costs, which is far cheaper than running a replica database.
3
Select the compute provisioning method that meets the RTO at the lowest cost.
Choose on-demand provisioning using AWS CloudFormation templates stored in S3.
AWS CloudFormation can provision the application tier in minutes, easily meeting the 44-hour RTO while incurring zero ongoing compute costs prior to a failover event.

Key Concept

Disaster Recovery strategies on AWS range from Backup & Restore (lowest cost, highest RTO/RPO) to Active-Active (highest cost, lowest RTO/RPO). A Backup & Restore approach utilizes offline resources like snapshots and infrastructure-as-code templates to minimize running costs.
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Topics

Multi-AZ, Multi-Region Architectures and Disaster Recovery (DR)

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