How do you implement cloud disaster recovery and business continuity?

Disaster recovery (DR) ensures business continuity during outages. RTO (Recovery Time Objective): maximum acceptable downtime. RPO (Recovery Point Objective): maximum acceptable data loss. DR tiers: (1) Backup and restore: lowest cost, highest RTO/RPO (hours), automated backups to another region, restore infrastructure from IaC and data from backups. (2) Pilot light: critical components always running in DR region (database replicas, identity services), other components launched from pre-built AMIs/containers on failover. (3) Warm standby: scaled-down but fully functional environment in DR region, scale up on failover. (4) Multi-site active-active: full capacity in multiple regions, traffic routed to nearest/healthiest region, automatic failover. Implementation: automate everything (IaC for infrastructure, scripts for failover procedures, automated health checks for failover triggers). Database DR: continuous replication to DR region (RDS cross-region replicas, Aurora Global Database), implement point-in-time recovery capability, and test restore procedures regularly. Data backup: implement 3-2-1 rule (3 copies, 2 different media types, 1 offsite), encrypt backups, test restore procedures monthly, and maintain documented recovery runbooks. Failover automation: health check monitoring detects primary region failure, DNS-based failover (Route53 health checks) or global load balancer routing, automated infrastructure scaling in DR region, and data promotion (promote read replica to primary). Testing: conduct DR drills quarterly, document lessons learned and update procedures, measure actual RTO/RPO versus targets, and implement chaos engineering to test resilience proactively. Cost optimization: use spot instances for warm standby, leverage reserved capacity for active-active, and implement automated scale-down in DR region during normal operations.