What is AWS multi-region and disaster recovery strategies?

AWS disaster recovery (DR) strategies, from cheapest to most expensive: 1. Backup and Restore (RTO: hours, RPO: hours): back up data to another region (S3 cross-region replication, RDS cross-region snapshots, EC2 AMI copy). On disaster: restore from backup in DR region. Cost: only backup storage. Lowest cost, longest recovery time. Use for non-critical systems. 2. Pilot Light (RTO: minutes to hours, RPO: minutes): minimal version of core infrastructure always running in DR region (RDS replica, critical servers). On disaster: scale up the pilot light infrastructure. Database already in sync (near real-time replication). Slightly more expensive than backup/restore. 3. Warm Standby (RTO: minutes, RPO: seconds to minutes): scaled-down but fully functional copy in DR region. Receives real-time data replication. On disaster: scale up to full production capacity. Route 53 health checks + failover routing for automatic DNS switch. Good balance of cost and recovery speed. 4. Multi-Site Active/Active (RTO: near zero, RPO: near zero): full production load in multiple regions simultaneously. Route 53 latency-based or geolocation routing distributes traffic. Both regions fully sized. Expensive — double infrastructure cost. Use for mission-critical applications. Key services for DR: Route 53 health checks + failover; S3 CRR; RDS read replicas + promotion; Global Aurora (cross-region replication with <1s RPO); DynamoDB Global Tables (active-active, multi-region); CloudFormation (recreate infrastructure from code); AMI copying across regions; Elastic Disaster Recovery (DRS — continuous server replication). RTO (Recovery Time Objective) = max acceptable downtime. RPO (Recovery Point Objective) = max acceptable data loss.