SAA-C03 Design Resilient Architectures Practice Question
A solutions architect is designing a highly available relational database tier for a customer-facing order system that must survive the loss of an entire Availability Zone with minimal administrative effort and no application connection-string changes during failover. (Choose two.)
⚠ Common exam trap
The trap here is assuming read replicas provide automatic failover; RDS read replicas replicate asynchronously and promoting one requires a manual step and can lose recent writes.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable a Multi-AZ DB cluster deployment for the RDS database so a writer and two readable standbys span three Availability Zones
Both Multi-AZ deployment types keep a synchronous standby copy of the data in another Availability Zone and expose a stable endpoint that survives automatic failover, which removes the need to edit connection strings. A Multi-AZ DB cluster goes further by adding two readable standbys across three zones and offering faster failover. The remaining choices rely on asynchronous replicas, manual promotion, or snapshot restores that all require operator action.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create manual read replicas in each Availability Zone and repoint the application to a replica after failover
Why it's wrong here
Read replicas use asynchronous replication, so a promoted replica can lose recently committed transactions, and the application would need its connection string changed to reach the new primary. That repointing is manual administration and risks data loss for an order system. Read replicas are appropriate for read scaling, not for transparent, low-loss failover of the primary endpoint.
- ✓
Enable a Multi-AZ DB cluster deployment for the RDS database so a writer and two readable standbys span three Availability Zones
Why this is correct
A Multi-AZ DB cluster runs one writer and two readable standbys across three Availability Zones and provides a single writer endpoint plus a reader endpoint. Failover is automatic and typically faster than a Multi-AZ DB instance, and the endpoint remains stable, so the application is unaffected. This meets the zone-failure and no-connection-string-change requirements.
- ✗
Store the database on an EC2 instance with an EBS volume and take nightly snapshots to a second Availability Zone
Why it's wrong here
Self-managed databases on EC2 require the architect to detect failure, launch a replacement, restore a snapshot, and reconfigure the application, all of which are manual and slow. Nightly snapshots also mean up to a day of lost transactions. This approach does not meet the minimal-administration or transparent-failover requirements of the order system.
- ✓
Deploy the database as an Amazon RDS Multi-AZ DB instance so a standby is maintained in a second Availability Zone
Why this is correct
A Multi-AZ DB instance deployment maintains a synchronous standby in a different Availability Zone and exposes a single DNS endpoint that the application continues to use. If the primary zone fails, Amazon RDS automatically promotes the standby and updates the endpoint, so no connection-string edit is needed. This directly satisfies the zone-failure and minimal-administration requirements.
- ✗
Rely on the RDS automated backup retention window to restore the instance into a different Availability Zone during an outage
Why it's wrong here
Restoring from an automated backup creates a new database instance with a new endpoint, and the restoration process takes time while the application is down. The application would then need to be repointed, which is exactly the manual change the design must avoid. Backup retention is a recovery mechanism, not a transparent high-availability failover mechanism.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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