SAA-C03 Design High-Performing Architectures Practice Question
A solutions architect is designing a caching layer for a high-traffic web application that uses a multi-node cluster. The architect needs to ensure high availability and the ability to scale horizontally while supporting complex data types such as sorted sets and lists. Which TWO features of Amazon ElastiCache for Redis support these requirements?
⚠ Common exam trap
SAA-C03 often tests the distinction between Redis and Memcached features, and candidates incorrectly select multi-threaded execution (a Memcached trait) or UDP as a Redis capability.
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
✓
Multi-AZ with automatic failover.
Option A (Multi-AZ with automatic failover) is correct because ElastiCache for Redis supports replication groups with a primary node and one or more read replicas across Availability Zones; if the primary fails, ElastiCache automatically promotes a replica, providing the high availability the multi-node cluster requires. Option C (Redis Cluster mode for horizontal scaling) is correct because cluster mode shards data across up to 500 shards (nodes), enabling horizontal scaling of both storage and throughput while still supporting complex Redis data structures such as sorted sets and lists. Option B is not correct because ElastiCache for Redis is fundamentally single-threaded for command execution (multi-threaded I/O exists in some versions, but it is not the feature that delivers HA or horizontal scaling here). Option D is not correct because ElastiCache does not provide automatic data compression at the cache level as a feature for this scenario. Option E is not correct because Redis communicates over TCP, not UDP, and UDP would not provide reliable low-latency writes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Multi-AZ with automatic failover.
Why this is correct
This feature provides high availability by automatically detecting a primary node failure and promoting a replica to primary in a different Availability Zone. This minimizes downtime and ensures that the caching layer remains performant and available even during infrastructure failures in a single zone.
- ✗
Support for multi-threaded execution.
Why it's wrong here
Redis is primarily a single-threaded engine for command execution, although recent versions have introduced some background threading for I/O. Memcached is typically the choice for multi-threaded performance, but it lacks the complex data structures and high availability features like Multi-AZ and replication required in this scenario.
- ✓
Redis Cluster mode for horizontal scaling.
Why this is correct
Redis Cluster mode allows data to be partitioned across multiple shards. This enables the cache to scale horizontally by adding more shards, providing increased memory capacity and throughput. This is essential for high-performing applications that outgrow the capacity of a single primary node.
- ✗
Automatic data compression at the cache level.
Why it's wrong here
Amazon ElastiCache does not provide native automatic data compression at the service level. Compression is typically handled by the application code before the data is sent to the cache. Relying on the cache for compression would introduce unnecessary latency and CPU overhead on the cache nodes.
- ✗
Use of UDP protocol for low-latency writes.
Why it's wrong here
Redis uses the TCP protocol to ensure reliable delivery of data and commands. While UDP can be faster in some networking contexts, it is not supported by ElastiCache for Redis because reliability and data integrity are paramount for a persistent data store and caching engine.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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.