SAA-C03 Design Resilient Architectures Practice Question
This SAA-C03 practice question tests your understanding of design resilient architectures. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Amazon RDS for PostgreSQL
DB instance identifier: orders-db
Multi-AZ: false
Automated backups: enabled
Availability Zone: us-east-1b
Publicly accessible: no
Based on the exhibit, the database must continue serving if the current Availability Zone fails. What should you change?
Amazon RDS for PostgreSQL
DB instance identifier: orders-db
Multi-AZ: false
Automated backups: enabled
Availability Zone: us-east-1b
Publicly accessible: no
A
Create a read replica in another Availability Zone and promote it manually if needed.
Why wrong: A read replica can help with read scaling or disaster recovery, but manual promotion is not the same as automatic failover. It adds operational delay.
B
Modify the DB instance to use a Multi-AZ deployment.
A Multi-AZ RDS deployment provides synchronous standby replication in another Availability Zone and automatic failover if the primary AZ becomes unavailable. This directly matches the requirement to keep the database serving after an AZ failure. It is the simplest resilient design change when the application needs high availability rather than just backups.
C
Increase the automated backup retention period to 30 days.
Why wrong: Longer backup retention helps with recovery from deletion or corruption, but it does not keep the database online during an Availability Zone failure. Backups are not failover.
D
Resize the DB instance to a larger class.
Why wrong: A larger instance may improve performance, but it does not protect against the loss of the Availability Zone. The same single point of failure would remain.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Modify the DB instance to use a Multi-AZ deployment.
Option B is correct because Multi-AZ deployment automatically provisions and maintains a synchronous standby replica in a different Availability Zone. If the primary AZ fails, Amazon RDS automatically fails over to the standby, ensuring database availability without manual intervention. This meets the requirement of continuing service during an AZ failure.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 a read replica in another Availability Zone and promote it manually if needed.
Why it's wrong here
A read replica can help with read scaling or disaster recovery, but manual promotion is not the same as automatic failover. It adds operational delay.
✓
Modify the DB instance to use a Multi-AZ deployment.
Why this is correct
A Multi-AZ RDS deployment provides synchronous standby replication in another Availability Zone and automatic failover if the primary AZ becomes unavailable. This directly matches the requirement to keep the database serving after an AZ failure. It is the simplest resilient design change when the application needs high availability rather than just backups.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the automated backup retention period to 30 days.
Why it's wrong here
Longer backup retention helps with recovery from deletion or corruption, but it does not keep the database online during an Availability Zone failure. Backups are not failover.
✗
Resize the DB instance to a larger class.
Why it's wrong here
A larger instance may improve performance, but it does not protect against the loss of the Availability Zone. The same single point of failure would remain.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing read replicas (which are for read scaling and asynchronous replication) with Multi-AZ (which is for high availability and synchronous replication), leading candidates to choose Option A for failover scenarios.
Detailed technical explanation
How to think about this question
Multi-AZ deployments use synchronous replication to a standby instance in a different AZ, with automatic failover handled by Amazon RDS via DNS record updates (CNAME swap). The failover typically completes within 1-2 minutes, and the standby is kept in sync with the primary using the same storage engine (e.g., InnoDB for MySQL). In a real-world scenario, this is critical for production databases that must meet SLAs for availability, as it protects against both AZ outages and instance-level failures.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Design Resilient Architectures — This question tests Design Resilient Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Modify the DB instance to use a Multi-AZ deployment. — Option B is correct because Multi-AZ deployment automatically provisions and maintains a synchronous standby replica in a different Availability Zone. If the primary AZ fails, Amazon RDS automatically fails over to the standby, ensuring database availability without manual intervention. This meets the requirement of continuing service during an AZ failure.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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