SOA-C02 Reliability and Business Continuity Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Deploy the RDS instance in a Multi-AZ configuration with automatic failover.

  Why this is correct

  Multi-AZ RDS uses synchronous replication to a standby instance in a different Availability Zone; every transaction is committed on both the primary and standby before being acknowledged, giving an RPO of zero. Should the primary fail, AWS automatically flips the DNS endpoint to the standby, typically completing failover in 60–120 seconds, comfortably meeting a 1-hour RTO. This makes it the only option that satisfies both the 5-minute RPO and the 1-hour RTO without manual intervention.

• ✗

  Use AWS Backup to copy snapshots to a different AWS Region.

  Why it's wrong here

  AWS Backup can copy RDS snapshots to another Region for disaster recovery, but snapshots are point-in-time captures taken on a scheduled interval (commonly daily or at most every few hours). That means you could lose up to the interval's worth of transactions, easily exceeding the 5-minute RPO requirement, and restoring a snapshot to a new instance typically takes well over an hour, missing the 1-hour RTO. Cross-Region snapshot copy is a batch displacement mechanism, not a live replication or automatic failover solution.

• ✗

  Take manual snapshots every 5 minutes and store them in Amazon S3.

  Why it's wrong here

  Taking a manual RDS snapshot every 5 minutes is operationally untenable because RDS limits the total number of snapshots per instance and snapshot creation itself is an asynchronous operation that can take longer than the interval, causing overlapping snapshot requests and potential throttling. Moreover, even though snapshots are stored in S3 under the hood, restoring from any snapshot requires creating a whole new RDS instance, with time-to-restore often exceeding the 1-hour RTO. Thus, frequent snapshots cannot provide the low RTO needed for automatic failover.

• ✗

  Configure a cross-region read replica and promote it during failover.

  Why it's wrong here

  A cross-Region read replica replicates asynchronously from the primary, so replication lag can vary from seconds to minutes depending on network conditions and workload, making it impossible to guarantee an RPO of 5 minutes. Promotion of a replica to a standalone primary is a manual or scripted operation that requires updating application connection strings, and the promotion itself can take several minutes, so it does not meet the 1-hour RTO as a robust automatic solution. While replicas are excellent for read scaling and disaster recovery with relaxed tolerance, they are not synchronous and do not offer the same zero-data-loss automatic failover as Multi-AZ.

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