AWS Certified Solutions Architect Professional SAP-C02 Practice Question
A company is running its core accounting system on Amazon RDS for PostgreSQL in the us-east-1 Region. The operations team has set several reliability goals. The database must survive the loss of an entire Availability Zone with zero data loss (RPO = 0) and automatically fail over in less than 60 seconds (RTO ≤ 60 s). During quarterly financial reporting when read traffic triples, the solution must absorb the surge without introducing more than 5 seconds of replication lag. Finally, the solution must minimize operational effort; custom promotion or fail-back scripts are not acceptable.
Which deployment option meets all these requirements?
Deploy an RDS Multi-AZ DB cluster with one writer and two readable standby instances across three AZs, and use the cluster's reader endpoint for reporting queries.
Provision a cross-Region read replica in us-west-2, enable automatic promotion, and route all read traffic to this replica during reporting periods.
Keep the single-AZ instance and schedule automated snapshots every 5 minutes to Amazon S3. Restore from the latest snapshot if an AZ outage occurs.
Create a Multi-AZ DB instance and add two read replicas in different AZs. Send read traffic to the replicas.
An Amazon RDS Multi-AZ DB cluster places one writer and two reader DB instances in three separate AZs. The engine uses semisynchronous replication that waits for at least one reader to acknowledge each commit, so no committed transaction can be lost (RPO = 0). Amazon RDS monitors the cluster and automatically promotes the reader with the latest changes; failovers are typically finished in under 35 seconds, satisfying the RTO target. Because the two standbys are "hot" and share a reader endpoint, applications can offload surging SELECT workloads with only single-digit-second lag and without any administrative work.
The other options fail one or more requirements:
A Multi-AZ DB instance plus read replicas uses asynchronous replication to the replicas and requires manual promotion, so it cannot guarantee RPO = 0, sub-5-second lag, or automatic failover.
Periodic snapshots offer neither the required RPO/RTO nor automatic failover.
A cross-Region read replica is designed for regional, not AZ, failure and still uses asynchronous replication; it adds latency and operational complexity without meeting the stated objectives.
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