Database DR differs fundamentally from all other layers. Web servers die, restart—that's all. Data lost once is lost forever. Database replication method determines system RPO at the most fundamental design level, with physics (light speed) and theory (consensus) imposing hard limits. AWS solved this via three paths—RDS, Aurora, DynamoDB—each selecting trade-offs that are exam essentials.
SAP-C02 in this domain isn't simple memorization ("Aurora Global spans 5 regions") but asking which chose sync/async replication, thus how RPO/RTO/consistency/writable regions split