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Difficulty: MediumDisaster Recovery Strategies

A company hosts a production three-tier web application in the us-east-1 Region. The database tier uses an Amazon Aurora PostgreSQL DB cluster. A SysOps administrator must implement a cross-region disaster recovery (DR) strategy in the us-west-2 Region. The strategy must achieve a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 5 minutes while minimizing ongoing running costs in the us-west-2 Region. Which disaster recovery strategy should the administrator implement to meet these requirements?

  1. Configure an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2. Deploy an Application Load Balancer and an Auto Scaling group with the capacity set to 0 in us-west-2. Configure an Amazon Route 53 active-passive failover routing policy with health checks pointing to the primary application. During a failover, promote the secondary cluster and scale up the Auto Scaling group.Answer
  2. B
    Configure Amazon RDS with a cross-region Read Replica in us-west-2. Configure the database with Multi-AZ enabled so that AWS automatically performs a synchronous failover and redirects write traffic to the us-west-2 replica during a primary region outage.
  3. C
    Configure Amazon S3 Cross-Region Replication (CRR) to replicate application configuration files to us-west-2 without enabling S3 Versioning on the source and destination buckets. Replicate Amazon RDS daily snapshots to us-west-2 and restore them manually during a disaster.
  4. D
    Configure Amazon Aurora Global Database across both Regions. Set up Amazon Route 53 with an active-active weighted routing policy to distribute traffic equally between us-east-1 and us-west-2 without DNS health checks to ensure seamless user failover if us-east-1 goes down.

Answer

Configure an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in us-west-2, set the Auto Scaling group capacity in us-west-2 to 0, configure a Route 53 active-passive failover routing policy with health checks, and promote the secondary cluster and scale up the Auto Scaling group during a failover.
The correct strategy implements a Pilot Light disaster recovery pattern. Amazon Aurora Global Database provides sub-second cross-region replication, matching the RPO of 5 minutes. Keeping the recovery region Auto Scaling group size at 0 minimizes ongoing compute costs, and both scaling up the instances and promoting the secondary Aurora database cluster can be completed within the 15-minute RTO. Route 53 active-passive failover routing automatically detects primary region failures and directs traffic to the secondary region once it is promoted.

Step-by-Step Solution

1
Evaluate the RPO requirement.
The RPO is 5 minutes, which requires continuous database replication. Aurora Global Database uses fast, physical, asynchronous replication that typically has a lag of less than one second, comfortably meeting the 5-minute RPO target.
Choosing a replication mechanism with latency under the RPO threshold is necessary to prevent data loss beyond 5 minutes.
2
Evaluate the RTO and cost requirements.
The RTO is 15 minutes, and running costs in the secondary region must be minimized. Deploying an Auto Scaling group with a desired capacity of 0 ensures no EC2 instances are running (minimizing costs), but they can be scaled up rapidly via scripts or CloudFormation during a disaster. Promoting the secondary Aurora DB cluster is also a fast operation that takes under 5 minutes.
This establishes a Pilot Light recovery model, which balances low standby cost with quick recovery times.
3
Determine the routing mechanism.
Route 53 active-passive failover routing with health checks must be used to detect outages in the primary region and direct users to the recovery region environment once it is scaled up and promoted.
Active-passive failover is necessary because the secondary database cannot accept writes under normal conditions, making active-active routing invalid.

Key Concept

Pilot Light Disaster Recovery Strategy
Estimated Time:2m 0s
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Topics

Disaster Recovery Strategies

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