SAA-C03 Design High-Performing Architectures Practice Question
A healthcare company runs a patient portal on Amazon EC2 instances behind an Application Load Balancer. The application stores session state in memory on each instance, and users are being logged out when the load balancer routes them to a different instance. The company wants to keep the application stateless and avoid modifying application code. Which solution best meets these requirements?
⚠ Common exam trap
The trap here is treating sticky sessions as a way to make an application stateless, when stickiness actually preserves state on a specific instance.
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 data in an Amazon ElastiCache for Redis cluster and have the instances read and write sessions there.
To keep an application stateless, session data must live outside the compute instances. ElastiCache for Redis provides a shared, low-latency session store that any instance can access, so users remain logged in regardless of which instance handles the request. Sticky sessions, warm pools, and cross-zone load balancing either mask the problem or address unrelated concerns without removing instance-local state.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure the Auto Scaling group to use a warm pool so that new instances inherit the session state from existing instances.
Why it's wrong here
A warm pool keeps pre-initialized instances ready to scale out, but it does not share in-memory session state between instances. Each instance still holds its own sessions, so users can still be logged out when routed elsewhere. Warm pools address launch latency, not session persistence, and they do not make the application stateless.
- ✓
Store session data in an Amazon ElastiCache for Redis cluster and have the instances read and write sessions there.
Why this is correct
Externalizing session state to ElastiCache for Redis removes session data from individual instances, making the application stateless. Any instance can serve any user because session data is shared and highly available. This meets the requirement without modifying application logic beyond the session store configuration, and it scales with the fleet.
- ✗
Enable sticky sessions on the Application Load Balancer using duration-based cookie stickiness.
Why it's wrong here
Sticky sessions bind a user to a specific target for the duration of the cookie, which can reduce logouts, but they do not make the application stateless. They also create uneven load distribution and can cause session loss if the target becomes unhealthy. The requirement explicitly asks to keep the application stateless, so stickiness is a workaround rather than a solution.
- ✗
Enable cross-zone load balancing on the Application Load Balancer to ensure sessions are distributed evenly.
Why it's wrong here
Cross-zone load balancing distributes traffic evenly across targets in all enabled Availability Zones, improving availability and balance. It does not share session state between instances, so users can still lose their sessions when routed to a different instance. This setting is unrelated to session persistence and does not satisfy the stateless requirement.
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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.