- A
Deploy a single-node Redis cluster and rely on application-level retries when cache misses occur.
Why wrong: A single-node setup has no automatic failover, so AZ impairment can fully break cache availability.
- B
Configure an ElastiCache Redis replication group with automatic failover across multiple Availability Zones.
Multi-AZ replication groups provide redundant nodes and automatic failover, improving cache resilience during AZ events.
- C
Move the cache into the VPC but keep it in one Availability Zone to reduce network latency.
Why wrong: Network placement does not address AZ-level redundancy; keeping one AZ still creates a single point of failure.
- D
Use a Memcached cluster and configure only client-side connection pooling without failover support.
Why wrong: Memcached differs operationally and connection pooling does not implement node-level failover in another AZ.
Quick Answer
The answer is to configure an ElastiCache Redis replication group with automatic failover across multiple Availability Zones. This design is correct because it creates a primary node in one AZ and one or more read-replicas in other AZs; if the primary or its AZ becomes impaired, automatic failover promotes a replica to primary, allowing the stateless web service to continue reading cached responses without interruption. On the SAA-C03 exam, this scenario tests your understanding of high-availability patterns for in-memory caches, often appearing alongside questions about RDS Multi-AZ or Aurora—but the key trap is that ElastiCache for Redis requires a replication group with automatic failover explicitly enabled, not just a single-node cluster. A common memory tip is to think of it as “Redis Replication + Multi-AZ = Automatic Failover,” and remember that read replicas in other AZs are the safety net for both planned maintenance and unplanned AZ impairments.
SAA-C03 Design Resilient Architectures Practice Question
This SAA-C03 practice question tests your understanding of design resilient architectures. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 caching layer uses Amazon ElastiCache for Redis in front of a stateless web service. The service must continue to read cached responses during maintenance events and should automatically fail over to another node if one AZ becomes impaired. Which design change best satisfies this requirement?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
Configure an ElastiCache Redis replication group with automatic failover across multiple Availability Zones.
Option B is correct because an ElastiCache Redis replication group with automatic failover across multiple Availability Zones ensures that if the primary node or its AZ becomes impaired, a read-replica in another AZ is automatically promoted to primary. This allows the stateless web service to continue reading cached responses without interruption, satisfying both the maintenance and AZ impairment requirements.
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.
- ✗
Deploy a single-node Redis cluster and rely on application-level retries when cache misses occur.
Why it's wrong here
A single-node setup has no automatic failover, so AZ impairment can fully break cache availability.
- ✓
Configure an ElastiCache Redis replication group with automatic failover across multiple Availability Zones.
Why this is correct
Multi-AZ replication groups provide redundant nodes and automatic failover, improving cache resilience during AZ events.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Move the cache into the VPC but keep it in one Availability Zone to reduce network latency.
Why it's wrong here
Network placement does not address AZ-level redundancy; keeping one AZ still creates a single point of failure.
- ✗
Use a Memcached cluster and configure only client-side connection pooling without failover support.
Why it's wrong here
Memcached differs operationally and connection pooling does not implement node-level failover in another AZ.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Memcached's simplicity with Redis's replication capabilities, assuming that client-side connection pooling alone can handle failover, when in fact Memcached lacks any built-in replication or automatic failover mechanism.
Detailed technical explanation
How to think about this question
ElastiCache Redis replication groups use asynchronous replication from the primary to up to five read replicas, with automatic failover triggered by a combination of health checks and the Redis Sentinel protocol. During failover, the DNS endpoint is updated to point to the new primary, and the client must use a Redis client that supports automatic reconnection and topology discovery (e.g., with the 'cluster-mode' or 'read-replica' configuration) to avoid stale connections. In a real-world scenario, if the primary node in us-east-1a fails, a replica in us-east-1b is promoted within seconds, and the web service's cache hit rate remains stable without manual intervention.
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
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
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: Configure an ElastiCache Redis replication group with automatic failover across multiple Availability Zones. — Option B is correct because an ElastiCache Redis replication group with automatic failover across multiple Availability Zones ensures that if the primary node or its AZ becomes impaired, a read-replica in another AZ is automatically promoted to primary. This allows the stateless web service to continue reading cached responses without interruption, satisfying both the maintenance and AZ impairment requirements.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on SAA-C03
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A caching layer uses Amazon ElastiCache for Redis in front of a stateless web service. The service must continue to read cached responses during maintenance events and should automatically fail over to another node if one AZ becomes impaired. Which design change best satisfies this requirement?
medium- A.Deploy a single-node Redis cluster and rely on application-level retries when cache misses occur.
- ✓ B.Configure an ElastiCache Redis replication group with automatic failover across multiple Availability Zones.
- C.Move the cache into the VPC but keep it in one Availability Zone to reduce network latency.
- D.Use a Memcached cluster and configure only client-side connection pooling without failover support.
Why B: Option B is correct because an ElastiCache Redis replication group with automatic failover across multiple Availability Zones ensures that if the primary node or its AZ becomes impaired, a read-replica in another AZ is automatically promoted to primary. This allows the stateless web service to continue reading cached responses during maintenance events without interruption, as the failover is transparent to the application.
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Last reviewed: Jun 11, 2026
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