AWS Disaster Recovery Strategies Explained

in Tutorials 29 min read

AWS Disaster Recovery: Complete Architecture Guide

Software developer at work
Software developer at work

AWS disaster recovery has gotten complicated with all the strategy options, service overlaps, and conflicting best practices flying around. As someone who has designed and tested DR architectures for multiple production environments — including one memorable incident where we actually had to failover for real — I learned everything there is to know about what works, what doesn’t, and what looks good on paper but falls apart under pressure. Today, I will share it all with you.

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Understanding RTO and RPO

Probably should have led with this section, honestly. Before you spend a single dollar on DR infrastructure, you need two numbers from your business stakeholders: your Recovery Time Objective (RTO) and your Recovery Point Objective (RPO). Everything else flows from these.

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Metric Definition Example
RTO (Recovery Time Objective) Maximum acceptable downtime after a disaster 4 hours = system must be online within 4 hours
RPO (Recovery Point Objective) Maximum acceptable data loss measured in time 1 hour = can lose up to 1 hour of data

Getting these numbers right matters more than most teams realize. I’ve seen organizations spend hundreds of thousands on multi-site active/active architectures when their actual business requirements would have been satisfied by a pilot light setup. I’ve also seen companies cheap out on backup-and-restore only to discover during an outage that their 24-hour RPO meant losing an entire day of customer orders. Have the conversation with stakeholders, get the numbers in writing, and design accordingly.

The Four DR Strategies

That’s what makes AWS DR endearing to us architects — there are four well-defined strategies that cover the entire spectrum from cheapest-and-slowest to most-expensive-and-fastest. You pick the one that matches your RTO/RPO requirements and budget, and AWS gives you the building blocks to implement it.

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Implementation:

  • Use AWS Backup for automated, policy-driven backups across services
  • Store backups in S3 with cross-region replication enabled
  • Maintain CloudFormation or Terraform templates for all infrastructure
  • Document and test recovery runbooks at least quarterly
# AWS Backup plan using Terraform
resource "aws_backup_plan" "dr_backup" {
  name = "disaster-recovery-plan"

  rule {
    rule_name         = "daily-backups"
    target_vault_name = aws_backup_vault.dr_vault.name
    schedule          = "cron(0 5 ? * * *)"  # Daily at 5 AM UTC

    lifecycle {
      delete_after = 30  # Retain for 30 days
    }

    copy_action {
      destination_vault_arn = aws_backup_vault.dr_vault_secondary.arn
      lifecycle {
        delete_after = 30
      }
    }
  }
}

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

Pilot light keeps a minimal version of your environment running continuously in the DR region. Think of it like a gas furnace — the pilot light is always on, and when you need heat, you ignite the main burners. Your core data services (databases, domain controllers) stay running and replicated, while everything else (app servers, web servers) exists only as templates ready to be launched.

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Architecture Pattern:

  1. Always Running: RDS read replica, minimal EC2 for replication
  2. Scaled Down: Auto Scaling groups set to 0 desired capacity
  3. On Failover: Promote read replica, scale up ASG, update Route 53 DNS
# 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
                    }
                }
            }]
        }
    )

I used pilot light for a mid-sized SaaS application and found the sweet spot was keeping the database replica and a single bastion host running in the DR region. Monthly cost was about $200, and we could fail over in under 15 minutes. That’s a remarkable cost-to-recovery ratio for a business that needed sub-hour RTO but couldn’t justify the expense of warm standby.

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

Warm standby runs a scaled-down but fully functional copy of your production environment in the DR region. Everything is active and receiving replicated data — you just run fewer and smaller instances than production.

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Key Technologies:

DR Strategy Comparison

Here’s the summary table I share with every client when we’re deciding on a DR approach. The right choice depends entirely on your business requirements and budget constraints:

Strategy RTO RPO Cost Complexity
Backup & Restore Hours Hours $ Low
Pilot Light 10s of minutes Minutes $$ Medium
Warm Standby Minutes Seconds $$$ Medium-High
Multi-Site Active/Active Near-zero Near-zero $$$$ High

AWS Services for DR

AWS Elastic Disaster Recovery (DRS)

Formerly CloudEndure, DRS provides continuous block-level replication of your source servers to AWS. I like it for lift-and-shift DR scenarios where you need to replicate on-premises or other-cloud servers to AWS without re-architecting them. The agent-based approach means you install a lightweight replication agent on each source server, and it continuously ships block-level changes to staging resources in your DR region.

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David Patel

David Patel

Author & Expert

Cloud Security Architect with expertise in AWS security services, compliance frameworks, and identity management. AWS Certified Security Specialty holder. Helps organizations implement zero-trust architectures on AWS.

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