In active-passive architecture, one region serves primary traffic and another is prepared for failover. It is simpler to reason about writes but requires tested promotion, routing, and recovery. The passive region may be cold, warm, or nearly ready depending on cost and RTO.

Active-active serves traffic from multiple regions simultaneously. It can reduce latency and improve regional availability, but writes to the same data create conflict, coordination, or ownership questions. Common strategies include assigning each entity a home region, partitioning writes by geography, or using a database with a defined multi-region consistency model.

Do not confuse duplicated compute with a complete active-active system. Sessions, queues, rate limits, scheduled jobs, secrets, search indexes, and external integrations also need regional behavior. Test split-brain and partial-region failures, not only total region shutdown.