1. Core Principles of Multi-Region Resilience
Building true High Availability (HA) requires zero shared single points of failure across failure domains.
By isolating control planes per region and using asynchronous replication for stateful tiers, regional outages are contained without cascading globally.
2. Stateful Replication & Read Replica Lag
Cross-region database replication introduces physics: speed of light latency between APAC and US-East means synchronous writes will degrade user P99.
We structure stateful services with local read replicas and asynchronous transactional replication pools with strict conflict resolution strategies.

