SAA-C03 Design High-Performing Architectures Practice Question
A company runs a stateless web application on Amazon EC2 instances behind an Application Load Balancer. The application stores session state in a relational database, which is becoming a bottleneck during peak hours. The team wants to improve performance and reduce database load while keeping the application stateless. Which solution should a solutions architect recommend?
⚠ Common exam trap
The trap here is assuming that sticky sessions or a larger database solve session state performance, when the real issue is that session data should be moved out of the relational database into a low-latency shared cache.
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
✓
Store session state in an Amazon ElastiCache for Redis cluster and configure the application to read and write sessions to the cluster.
Externalizing session state to an in-memory cache such as ElastiCache for Redis removes the relational database bottleneck and keeps the application stateless. Redis provides sub-millisecond latency, high throughput, and optional persistence, making it ideal for session stores. Sticky sessions or database scaling do not achieve the same performance and scalability benefits.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Migrate the session table to Amazon DynamoDB with on-demand capacity and update the application to use DynamoDB for session storage.
Why it's wrong here
DynamoDB can store session state and scale well, but it introduces higher latency than an in-memory cache for session reads and writes. It also adds cost and complexity for a workload that benefits more from a caching layer. While viable, it is not the optimal choice for reducing database bottleneck and improving performance for frequently accessed session data.
- ✓
Store session state in an Amazon ElastiCache for Redis cluster and configure the application to read and write sessions to the cluster.
Why this is correct
ElastiCache for Redis provides low-latency, in-memory session storage that scales horizontally and removes the database bottleneck. The application remains stateless because session data is externalized to a shared, highly available cache. This improves response times and reduces relational database load during peak traffic, which is a standard pattern for session management.
- ✗
Increase the size of the relational database instance and add read replicas, then direct session reads to the replicas and writes to the primary.
Why it's wrong here
Scaling the database and adding read replicas can help with read-heavy workloads, but session writes still go to the primary, and replication lag may cause stale session reads. This does not eliminate the database as a bottleneck and adds cost. It also does not externalize session state as effectively as an in-memory cache.
- ✗
Enable sticky sessions on the Application Load Balancer and store session state in the local memory of each EC2 instance.
Why it's wrong here
Sticky sessions tie users to specific instances, which can cause uneven load distribution and session loss if an instance fails. Storing sessions locally also makes the application stateful, contradicting the requirement. This approach does not reduce database load in a scalable way and harms availability and elasticity.
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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 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.