Design a multi-region, highly available deployment for a service requiring 99.99% uptime.

Cover: active-active vs. active-passive trade-off discussion tied to the specific RTO/RPO targets; load balancing/traffic routing across regions (global load balancer or DNS-based failover); data layer strategy for cross-region consistency (this is usually the hardest part — discuss whether the data model can tolerate eventual consistency or requires a single-writer-region approach); independent per-region health monitoring with automated failover; and explicit acknowledgment that 99.99% (about 52 minutes of downtime/year) requires eliminating essentially every single point of failure, includi