A global order service needs low-latency reads near users, but all writes must preserve a single relational transaction boundary. Regional recovery must have a small data-loss window. Which database design best fits these stated constraints?

1. Use independent writable relational databases in every Region with no conflict protocol.
2. Use S3 replication as a synchronous replacement for relational transactions.
3. Use one ordinary single-AZ RDS instance and only change DNS on regional failure.
4. Use Aurora Global Database with a primary write Region and regional read clusters, plus a tested promotion runbook.