Multi-Region Failover Architecture — AWS Solutions Architect Pro (SAP-C02)
'No Region as SPOF' Points to Active-Active, Not Passive Standby
Passive standby with Route 53 health checks and automated promotion handles RTOs measured in minutes at substantially lower cost than active-active. It still has a recovery step: DNS propagation, read replica promotion, or compute scaling before the standby region can serve traffic. Active-active with DynamoDB Global Tables, Aurora Global Database, and latency-based or weighted routing has no failover step because both regions serve traffic at all times. The phrase 'no region can be a single point of failure' or a stated RTO near zero rules out passive standby. When the scenario accepts a few minutes of recovery time, passive standby is the economically correct answer.
What This Pattern Tests
The exam describes global availability and tests active-active vs. active-passive design. Active-active (DynamoDB Global Tables, Aurora Global Database write forwarding) serves traffic from both regions simultaneously — lower latency for global users but requires conflict resolution for concurrent writes. Active-passive (Route 53 failover, Aurora Global Database with read-only secondary) serves from one region and fails over — simpler consistency but RTO depends on failover detection and promotion time. The trap is choosing active-active without addressing write conflicts or active-passive when the scenario requires zero-downtime global access.
Decision Axis
Data consistency requirements (eventual vs. strong) and latency needs (global vs. regional) determine active-active vs. active-passive.
Associated Traps
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Decision Rules
Warm standby (Aurora Global Database + AWS Elastic Disaster Recovery + Route 53 health checks) is the minimum sufficient DR tier for RTO < 15 minutes and RPO < 1 minute; multi-site active/active satisfies the same thresholds at materially higher continuous cost with no additional constraint benefit, making it an unjustified over-provision under an explicit cost constraint.
Domain Coverage
Difficulty Breakdown