A second region looks like an availability feature on an architecture diagram. In production it is a recurring operating commitment. Teams must decide where writes happen, which signal authorizes failover, how callbacks and queues behave, and who keeps the secondary environment healthy every month.
Name the failure you intend to survive
A zonal outage, regional service failure, network partition and operator mistake need different designs. State the protected user flow and acceptable recovery time before choosing active-active or active-passive.
Keep write authority narrow
Order numbers, inventory and access changes carry ordering and conflict rules. Multiple read locations are easy; multiple write locations require a business conflict policy.
Automatic failover needs multiple signals
Combine customer request success, durable write health and network reachability. DNS changes do not remove existing connections, callbacks or message consumers, so test the full path rather than the web endpoint alone.
Give the secondary region routine work
Run internal reads or lower-priority jobs there and exercise failover on a schedule. Include patching, capacity, data transfer and drills in the ongoing cost, not only the initial build.