SAA-C03 Design Resilient Architectures Practice Question
An application uses an Amazon Aurora DB cluster. The cluster performs an automatic failover from the writer instance to a standby instance. After failover completes, reads succeed, but all new writes fail with errors indicating the application is connecting to the old writer endpoint. Which change best fixes the resiliency issue after failover?
⚠ Common exam trap
Many exam-takers confuse instance-specific endpoints with cluster endpoints, assuming that failover automatically updates all DNS records, but only the cluster endpoint is dynamically updated to reflect the new writer.
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
✓
Update the application to use the Aurora cluster writer endpoint (or the cluster endpoint intended for writes) rather than an instance-specific endpoint.
The application is failing writes because it is connecting to the old writer instance's endpoint, which is no longer the writer after failover. The Aurora cluster writer endpoint is a DNS name that always points to the current primary (writer) instance, regardless of failovers. By using the cluster writer endpoint, the application automatically connects to the new writer after failover, eliminating the need to manually update connection strings.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Update the application to use the Aurora cluster writer endpoint (or the cluster endpoint intended for writes) rather than an instance-specific endpoint.
Why this is correct
During Aurora failover, the writer role moves to a different underlying DB instance. The cluster writer endpoint is stable and always resolves to the current writer, even after failover. An instance-specific endpoint continues to point to the original (now non-writer) instance, so write operations fail if the application keeps using that stale endpoint.
- ✗
Enable Multi-AZ on the individual writer instance settings so it can automatically create a new instance during failover.
Why it's wrong here
For Aurora, failover behavior and Multi-AZ/replication are managed at the cluster level. Changing an individual instance’s Multi-AZ settings does not correct the fundamental problem that the application is connecting to the wrong endpoint for the current writer role.
- ✗
Increase the failover timeout for Aurora to 60 minutes to ensure the app finishes reconnecting.
Why it's wrong here
Failover timeout affects how long Aurora may take to complete the failover process, but it does not fix the client-side endpoint selection. If the application continues to target the old writer instance endpoint, writes will keep failing after failover as well.
- ✗
Switch the cluster to a single-AZ configuration to reduce connection retries after failover.
Why it's wrong here
Switching Aurora to a single-AZ configuration removes the physical separation between the primary and replica instances, eliminating the very redundancy that makes failover meaningful. Aurora’s high availability relies on replicas in different Availability Zones; a single-AZ cluster would still fail over to a local replica (if any) or force a restart, but it cannot reduce client reconnection failures because the app is still pinned to a specific instance endpoint. Moreover, the write failure is caused by using the old writer endpoint after the role moves to another instance, which no AZ topology change can resolve. This option also sacrifices durability and availability guarantees, directly contradicting Aurora’s design for automatic failover and recovery.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.