Interview question: "Design disaster recovery for a payment system."
Multi-region patterns:
- Active-passive: Primary serves traffic, DR on standby
- Active-active: Both regions serve traffic
- Pilot light: Minimal DR infrastructure, scale up on failover
Recovery objectives:
- RTO: How long to recover?
- RPO: How much data loss is acceptable?
Data replication:
- Synchronous: No data loss, higher latency
- Asynchronous: Potential data loss, lower latency
Design approach: Define RTO/RPO requirements. Choose replication strategy. Design failover automation. Test regularly.