- A
Use Amazon Route 53 with weighted routing to distribute traffic between the two regions. Use a global DynamoDB table for session data, and launch EC2 instances in the DR region only when a failure is detected using AWS CloudFormation StackSets.
Why wrong: Weighted routing does not automatically failover; it requires manual adjustment. CloudFormation StackSets would take time to provision instances, likely exceeding the 1-hour RTO. Also, the requirement mentions ElastiCache Redis, not DynamoDB.
- B
Create a read replica of the ElastiCache Redis cluster in the DR region using the native cross-region replication feature. Use Route 53 with failover routing to point to the DR region ALB when the primary health check fails. Pre-configure EC2 instances in an Auto Scaling group in the DR region.
Global Datastore for Redis provides cross-Region replication with low RPO. Pre-configured Auto Scaling groups in the DR region ensure that compute capacity is ready. Route 53 failover routing automatically redirects traffic when the primary ALB health check fails. This combination meets the RPO and RTO requirements with minimal manual effort.
- C
Use an Amazon CloudFront distribution with multiple origins (primary and DR). Enable session stickiness at the CloudFront level. Use EC2 instances in both regions behind separate ALBs. No special data replication is needed because sessions are stored in Redis.
Why wrong: CloudFront does not provide cross-region failover for origins in the way Route 53 does. Session stickiness is not sufficient for DR because Redis data is not replicated across regions, so users would lose sessions after failover. RPO would be effectively longer than 15 minutes without replication.
- D
Use EC2 instances with an Auto Scaling group in both regions. Schedule a Lambda function to take snapshots of the Redis cluster every 15 minutes and copy them to the DR region. Use Route 53 latency routing to direct users to the nearest region.
Why wrong: Snapshot-based replication every 15 minutes could meet the RPO, but copying snapshots and restoring them during a disaster would take more than 1 hour, exceeding the RTO. Latency routing does not provide automatic failover in a regional outage; it routes based on latency, which could still send traffic to the failed region.
Quick Answer
The answer is to create a read replica of the ElastiCache Redis cluster in the DR region using native cross-region replication, paired with Route 53 failover routing and pre-configured EC2 instances in an Auto Scaling group. This works because ElastiCache Redis supports cross-region replication, which asynchronously replicates session data from the primary cluster to a read replica in the DR region, keeping the RPO under 15 minutes. Route 53’s failover routing automatically detects a primary region outage via health checks on the ALB and redirects traffic to the DR region’s pre-provisioned ALB and Auto Scaling group, achieving the 1-hour RTO with minimal manual effort. On the SOA-C02 exam, this scenario tests your understanding of combining managed caching replication with DNS-based traffic management for stateful DR. A common trap is assuming you must use Global Datastore for Redis (which is for active-passive, not read replicas) or relying on snapshot restore, which would exceed the RPO. Memory tip: “Replicate, Route, Ready” — cross-region read replica for data, Route 53 failover for traffic, and pre-scaled compute for capacity.
SOA-C02 Reliability and Business Continuity Practice Question
This SOA-C02 practice question tests your understanding of reliability and business continuity. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
A company runs a critical stateful web application on Amazon EC2 instances in a single AWS region. The application stores user session data in an Amazon ElastiCache for Redis cluster. The SysOps administrator must design a disaster recovery (DR) strategy that can survive a complete regional outage with a Recovery Point Objective (RPO) of 15 minutes and a Recovery Time Objective (RTO) of 1 hour. The application must be able to redirect users to the DR region with minimal manual effort. Which combination of actions meets these requirements?
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
Create a read replica of the ElastiCache Redis cluster in the DR region using the native cross-region replication feature. Use Route 53 with failover routing to point to the DR region ALB when the primary health check fails. Pre-configure EC2 instances in an Auto Scaling group in the DR region.
Option B is correct because ElastiCache for Redis supports cross-region replication via a read replica in the DR region, which can keep session data synchronized with minimal lag, meeting the 15-minute RPO. Route 53 failover routing with health checks on the primary region's ALB automatically redirects traffic to the pre-configured DR region EC2 instances and ALB, achieving the 1-hour RTO with minimal manual effort. Pre-configuring the DR region with an Auto Scaling group ensures compute capacity is ready, while the read replica provides the required data availability.
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.
- ✗
Use Amazon Route 53 with weighted routing to distribute traffic between the two regions. Use a global DynamoDB table for session data, and launch EC2 instances in the DR region only when a failure is detected using AWS CloudFormation StackSets.
Why it's wrong here
Weighted routing does not automatically failover; it requires manual adjustment. CloudFormation StackSets would take time to provision instances, likely exceeding the 1-hour RTO. Also, the requirement mentions ElastiCache Redis, not DynamoDB.
- ✓
Create a read replica of the ElastiCache Redis cluster in the DR region using the native cross-region replication feature. Use Route 53 with failover routing to point to the DR region ALB when the primary health check fails. Pre-configure EC2 instances in an Auto Scaling group in the DR region.
Why this is correct
Global Datastore for Redis provides cross-Region replication with low RPO. Pre-configured Auto Scaling groups in the DR region ensure that compute capacity is ready. Route 53 failover routing automatically redirects traffic when the primary ALB health check fails. This combination meets the RPO and RTO requirements with minimal manual effort.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use an Amazon CloudFront distribution with multiple origins (primary and DR). Enable session stickiness at the CloudFront level. Use EC2 instances in both regions behind separate ALBs. No special data replication is needed because sessions are stored in Redis.
Why it's wrong here
CloudFront does not provide cross-region failover for origins in the way Route 53 does. Session stickiness is not sufficient for DR because Redis data is not replicated across regions, so users would lose sessions after failover. RPO would be effectively longer than 15 minutes without replication.
- ✗
Use EC2 instances with an Auto Scaling group in both regions. Schedule a Lambda function to take snapshots of the Redis cluster every 15 minutes and copy them to the DR region. Use Route 53 latency routing to direct users to the nearest region.
Why it's wrong here
Snapshot-based replication every 15 minutes could meet the RPO, but copying snapshots and restoring them during a disaster would take more than 1 hour, exceeding the RTO. Latency routing does not provide automatic failover in a regional outage; it routes based on latency, which could still send traffic to the failed region.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume snapshot-based replication (Option D) is sufficient for a 15-minute RPO, but they overlook the inherent latency and potential data loss from periodic snapshots, and that latency routing (Option D) does not provide health-based failover, while weighted routing (Option A) lacks automatic failover capability.
Detailed technical explanation
How to think about this question
ElastiCache for Redis cross-region replication uses an asynchronous replication mechanism where the primary cluster in the source region sends write-ahead log (AOF) or replication stream data to the read replica in the DR region, typically achieving sub-second to few-second lag under normal conditions. Route 53 failover routing relies on DNS health checks that evaluate the health of the primary ALB endpoint; when the health check fails, the TTL on the DNS record (often 60 seconds) causes clients to re-resolve to the DR region, contributing to the RTO. Pre-configuring the DR region with an Auto Scaling group and ALB ensures that compute and network resources are ready, reducing recovery time to just DNS propagation and application warm-up.
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
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this SOA-C02 question test?
Reliability and Business Continuity — This question tests Reliability and Business Continuity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a read replica of the ElastiCache Redis cluster in the DR region using the native cross-region replication feature. Use Route 53 with failover routing to point to the DR region ALB when the primary health check fails. Pre-configure EC2 instances in an Auto Scaling group in the DR region. — Option B is correct because ElastiCache for Redis supports cross-region replication via a read replica in the DR region, which can keep session data synchronized with minimal lag, meeting the 15-minute RPO. Route 53 failover routing with health checks on the primary region's ALB automatically redirects traffic to the pre-configured DR region EC2 instances and ALB, achieving the 1-hour RTO with minimal manual effort. Pre-configuring the DR region with an Auto Scaling group ensures compute capacity is ready, while the read replica provides the required data availability.
What should I do if I get this SOA-C02 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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Last reviewed: Jun 11, 2026
This SOA-C02 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 SOA-C02 exam.
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