SAA-C03 Design Resilient Architectures Practice Question
A company hosts a web application on EC2 instances behind an Application Load Balancer. The application stores session state in local memory, causing users to be logged out whenever the load balancer routes requests to different instances. Which solution provides the most resilient, scalable architecture to resolve this?
⚠ Common exam trap
SAA-C03 often tests whether candidates recognize that stickiness and file replication are anti-patterns for scalable session management; the trap is choosing ALB stickiness as a quick fix instead of externalizing state to a managed in-memory store.
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 Amazon ElastiCache for Redis.
Storing session state in Amazon ElastiCache for Redis externalizes session data so any EC2 instance behind the ALB can serve any request, eliminating the logout problem while providing high availability and scalability. Redis is purpose-built for low-latency session stores and supports replication and failover. This is the AWS-recommended pattern for stateless web tiers.
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 Application Load Balancer to use source IP stickiness.
Why it's wrong here
Source IP stickiness ties a client to a specific backend instance. If that instance fails or the Auto Scaling group terminates it, the session state is lost. This approach creates a dependency on individual instance health, violating the principle of designing stateless, resilient application tiers.
- ✗
Use Amazon EBS multi-attach to share session files across instances.
Why it's wrong here
EBS volumes can only be attached to instances within the same Availability Zone. If the AZ fails, the data becomes inaccessible, creating a single point of failure. Furthermore, file-based locking mechanisms are inefficient and prone to corruption in high-concurrency environments compared to dedicated caching services.
- ✓
Store session state in Amazon ElastiCache for Redis.
Why this is correct
ElastiCache for Redis provides a high-performance, distributed, and managed key-value store that persists session data outside the web server memory. This ensures that session state remains available even when instances are replaced, enabling seamless horizontal scaling and maintaining high availability across multiple Availability Zones.
- ✗
Replicate session files using a cron job across all web instances.
Why it's wrong here
Replicating files via cron jobs introduces significant latency and synchronization challenges. As the number of instances grows, the overhead of maintaining consistency becomes unmanageable and error-prone. This design lacks the robustness and sub-millisecond performance required for modern, scalable, and resilient cloud-native web applications.
Visual reference
About these practice questions
Courseiva writes every SAA-C03 question from scratch — 149 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.