Design multi-region banking data synchronization

## System design: Global bank with multi-region data consistency A digital bank operates in multiple geographic regions (e.g., EU, US, APAC). Users can log in and perform operations (balance checks, transfers, card payments) from anywhere. ### Prompt Design a data architecture that keeps customer/account data consistent across regions. ### Requirements - High availability and low latency for reads (users worldwide). - Correctness for money movement (no double-spend). - Tolerate regional failures and network partitions. - Clear consistency model: what must be strongly consistent vs what can be eventually consistent. ### Discuss - Replication strategy (sync/async, leader-based vs multi-leader). - How to handle cross-region writes (especially transfers). - Conflict resolution and idempotency. - Operational concerns: recovery, reconciliation, auditing, observability.