- 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.
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?
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.
When this WOULD be correct
This option would be correct in a scenario where the application can tolerate cache unavailability (e.g., reads from a slower database are acceptable) and the primary goal is cost minimization, with no requirement for high availability or automatic failover.
- ✓
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.
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.
When this WOULD be correct
If the requirement was to minimize latency for a single-AZ application with no high availability needs, and the question explicitly stated that AZ impairment is not a concern, then deploying in one AZ would be appropriate.
- ✗
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.
When this WOULD be correct
If the requirement was for a simple, low-latency cache that can tolerate data loss and does not need automatic failover (e.g., caching non-critical, recomputable data in a single AZ), Memcached with client-side pooling would be appropriate.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.
✓Configure an ElastiCache Redis replication group with automatic failover across multiple Availability Zones.Correct answer▾
Why this is correct
Multi-AZ replication groups provide redundant nodes and automatic failover, improving cache resilience during AZ events.
✗Deploy a single-node Redis cluster and rely on application-level retries when cache misses occur.Wrong answer — click to see why▾
Why this is wrong here
A single-node Redis cluster lacks automatic failover; if the node or its AZ becomes impaired, the service cannot read cached responses until the node is restored, violating the requirement for continued reads during maintenance and AZ impairment.
★ When this WOULD be the correct answer
This option would be correct in a scenario where the application can tolerate cache unavailability (e.g., reads from a slower database are acceptable) and the primary goal is cost minimization, with no requirement for high availability or automatic failover.
Why candidates choose this
Candidates may think a single-node cluster is simpler and cheaper, and assume application-level retries are sufficient to handle failures, underestimating the need for automatic failover to maintain cache availability during AZ impairments.
✗Move the cache into the VPC but keep it in one Availability Zone to reduce network latency.Wrong answer — click to see why▾
Why this is wrong here
Keeping the cache in one Availability Zone does not provide automatic failover to another node if that AZ becomes impaired, failing the requirement for high availability during maintenance events.
★ When this WOULD be the correct answer
If the requirement was to minimize latency for a single-AZ application with no high availability needs, and the question explicitly stated that AZ impairment is not a concern, then deploying in one AZ would be appropriate.
Why candidates choose this
Candidates may think that reducing network latency by keeping the cache in one AZ is more important than high availability, or they may overlook the failover requirement and focus solely on performance.
✗Use a Memcached cluster and configure only client-side connection pooling without failover support.Wrong answer — click to see why▾
Why this is wrong here
Memcached does not support automatic failover or multi-AZ replication; if an AZ becomes impaired, the cache becomes unavailable, violating the requirement for continued reads during maintenance.
★ When this WOULD be the correct answer
If the requirement was for a simple, low-latency cache that can tolerate data loss and does not need automatic failover (e.g., caching non-critical, recomputable data in a single AZ), Memcached with client-side pooling would be appropriate.
Why candidates choose this
Candidates may confuse Memcached's simplicity and speed with high availability, or assume that client-side connection pooling alone provides failover, not realizing Memcached lacks built-in replication and automatic failover.
Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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.
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
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