SAP-C02 Continuous Improvement for Existing Solutions Practice Question
A company has a web application running on Amazon EC2 instances in an Auto Scaling group. The application stores session state in a self-managed Redis cluster on EC2 instances. During a recent marketing campaign, the Redis cluster became a bottleneck, causing session timeouts and lost carts. The company wants to improve the scalability and availability of the session store with minimal application changes. Which solution should a solutions architect recommend?
⚠ Common exam trap
The trap here is assuming that simply scaling up the self-managed Redis instances or switching to Memcached will solve the problem, without considering the need for horizontal scaling and automatic failover that ElastiCache for Redis provides.
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
✓
Migrate the session store to Amazon ElastiCache for Redis with cluster mode enabled and a Multi-AZ configuration.
The self-managed Redis cluster is a bottleneck and lacks high availability. Migrating to Amazon ElastiCache for Redis with cluster mode enabled provides horizontal scaling through sharding and Multi-AZ replication for automatic failover. Because ElastiCache is Redis-compatible, the application requires minimal changes, directly addressing both scalability and availability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the size of the EC2 instances in the self-managed Redis cluster and enable Redis Cluster mode.
Why it's wrong here
Scaling up the EC2 instances provides vertical scaling but does not address the need for high availability across AZs or the operational overhead of managing Redis. Enabling Redis Cluster mode on self-managed instances requires configuration changes and still leaves the company responsible for failover and maintenance. This does not meet the minimal-change and availability requirements as effectively as a managed service.
- ✗
Deploy an Amazon ElastiCache for Memcached cluster with Auto Discovery and enable Multi-AZ.
Why it's wrong here
ElastiCache for Memcached does not support Multi-AZ with automatic failover in the same way as Redis; it relies on client-side sharding and has no persistence. Migrating from Redis to Memcached would require code changes because the data structures and commands differ. Additionally, Memcached does not support replication or failover, so it would not improve availability as required.
- ✓
Migrate the session store to Amazon ElastiCache for Redis with cluster mode enabled and a Multi-AZ configuration.
Why this is correct
Amazon ElastiCache for Redis with cluster mode enabled supports sharding across up to 500 shards, providing horizontal scalability. Multi-AZ with automatic failover ensures high availability. The application can continue using the Redis protocol, so minimal changes are required. This directly addresses the bottleneck and availability issues observed during the campaign.
- ✗
Replace the self-managed Redis cluster with Amazon DynamoDB Accelerator (DAX) and store session data in DynamoDB.
Why it's wrong here
DAX is an in-memory cache for DynamoDB, not a Redis-compatible session store. Migrating to DynamoDB would require significant application changes to use the DynamoDB API instead of Redis commands. While DynamoDB is highly scalable, the scenario requires minimal application changes, and DAX does not support Redis data structures or commands, making it unsuitable.
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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 SAP-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 SAP-C02 exam.