Multi-Az And Data Durability Design — AWS Solutions Architect Pro (SAP-C02)
Multi-AZ RDS vs Aurora Global: AZ Failure vs Regional Failure
RDS Multi-AZ gets picked for high availability, but the standby replica sits in the same AWS region as the primary. A scenario requiring that data survives a full regional outage, or specifying a secondary recovery region for compliance, rules out Multi-AZ as the complete solution. Aurora Global Database maintains a secondary region with sub-second replication and supports promotion of that region to a writable endpoint. Cross-region read replicas on standard RDS can also be promoted manually when needed. SAP-C02 professional questions test this AZ-versus-region distinction most often in database resilience topics, and the wrong answer is consistently Multi-AZ paired with a regional failure requirement.
What This Pattern Tests
The exam tests AZ-level resilience as the baseline design pattern. RDS Multi-AZ deploys a synchronous standby in another AZ — automatic failover in 60-120 seconds, no data loss. Read Replicas use asynchronous replication — no automatic failover, potential data lag. EBS volumes are AZ-scoped — an AZ failure loses access to the volume. S3 stores objects across at least 3 AZs automatically. The trap is confusing Multi-AZ (high availability, synchronous) with Read Replicas (read scaling, asynchronous) or assuming EBS survives an AZ failure (it does not without snapshots).
Decision Axis
Availability target determines AZ design: 99.9% may need single-AZ with backups, 99.99% needs Multi-AZ, 99.999% needs Multi-Region.
Associated Traps
More Top Traps on This Exam
Decision Rules
Whether RPO < 1 hour and RTO < 4 hours mandates always-on cross-Region replication or is fully satisfied by multi-AZ Aurora with automated AWS Backup snapshots and Route 53 health-check failover.
Domain Coverage
Difficulty Breakdown