AWS Disaster Recovery: Pilot Light, Warm Standby & Multi-Site Strategies

AWS defines four disaster recovery strategies, ordered from lowest to highest cost and complexity:

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Implementation:

2. Pilot Light (RTO: 10s of Minutes | RPO: Minutes)

A minimal version of your environment runs continuously in the DR region. Core components (databases, domain controllers) are always on, while application servers are launched during failover.

# Pilot Light failover script (Python)
import boto3

def failover_to_dr(primary_region, dr_region):
    # 1. Promote RDS read replica
    rds = boto3.client('rds', region_name=dr_region)
    rds.promote_read_replica(
        DBInstanceIdentifier='mydb-replica'
    )

    # 2. Scale up Auto Scaling group
    autoscaling = boto3.client('autoscaling', region_name=dr_region)
    autoscaling.update_auto_scaling_group(
        AutoScalingGroupName='app-asg-dr',
        MinSize=2,
        DesiredCapacity=4
    )

    # 3. Update Route 53 to point to DR
    route53 = boto3.client('route53')
    route53.change_resource_record_sets(
        HostedZoneId='Z1234567890',
        ChangeBatch={
            'Changes': [{
                'Action': 'UPSERT',
                'ResourceRecordSet': {
                    'Name': 'app.example.com',
                    'Type': 'A',
                    'AliasTarget': {
                        'HostedZoneId': 'Z2FDTNDATAQYW2',
                        'DNSName': 'dr-alb.us-west-2.elb.amazonaws.com',
                        'EvaluateTargetHealth': True
                    }
                }
            }]
        }
    )

3. Warm Standby (RTO: Minutes | RPO: Seconds)

A scaled-down but fully functional copy of your production environment runs in the DR region. All components are active and receiving replicated data.