The answer is to migrate session data to ElastiCache for Redis and modify the application to use it. This is correct because storing session state locally on EC2 instances creates a tight coupling between user data and instance lifecycle, so when Auto Scaling terminates or launches instances, session data is lost, causing user logouts. By centralizing session state in ElastiCache, a fully managed, in-memory data store, the session persists independently of any single instance, enabling stateful Auto Scaling where any instance can serve any user without data loss. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of decoupling state from compute for elasticity, often appearing as a trap where candidates might incorrectly choose sticky sessions (which still lose data on instance failure) or a shared file system (which adds latency). Remember the memory tip: “State belongs in cache, not on the instance’s disk.”
SAP-C02 Continuous Improvement for Existing Solutions Practice Question
This SAP-C02 practice question tests your understanding of continuous improvement for existing solutions. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is running a stateful web application on EC2 instances in an Auto Scaling group behind an ALB. The application stores session data locally on the instance. The company notices that users are frequently logged out and lose session data during scaling events. What is the MOST operationally efficient way to preserve session state?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Migrate session data to ElastiCache for Redis and modify the application to use it.
Option A is correct because migrating session state to ElastiCache for Redis provides a centralized, external, and highly available session store that persists independently of EC2 instance lifecycles. This ensures that when instances are terminated or added during Auto Scaling events, session data remains intact and accessible from any instance, eliminating user logouts and data loss. It is operationally efficient as it requires minimal application code changes and leverages a fully managed, in-memory data store optimized for low-latency access.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 session data to ElastiCache for Redis and modify the application to use it.
Why this is correct
Externalizing session state ensures data persists across instance replacements.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a custom AMI that pre-populates session data from Amazon S3.
Why it's wrong here
Session data is dynamic and cannot be pre-populated in an AMI.
✗
Increase the Auto Scaling group's cooldown period to 600 seconds.
Why it's wrong here
Longer cooldown delays scaling, which can cause performance issues.
✗
Enable sticky sessions (session affinity) on the ALB.
Why it's wrong here
Sticky sessions route traffic to the same instance but do not protect against instance termination.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose sticky sessions (Option D) thinking it solves session persistence, but they overlook that sticky sessions only route traffic to the same instance and do not protect against data loss when that instance is terminated during scaling events.
Detailed technical explanation
How to think about this question
ElastiCache for Redis uses an in-memory key-value store with optional persistence (snapshots to S3) and replication across Availability Zones, providing sub-millisecond read/write latency. The application must be modified to use a Redis client (e.g., Redis-py, Jedis) to store and retrieve session data by a unique session ID, typically set as a cookie. Under the hood, Redis uses a single-threaded event loop for atomic operations, ensuring consistency even under concurrent access from multiple EC2 instances.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Migrate session data to ElastiCache for Redis and modify the application to use it. — Option A is correct because migrating session state to ElastiCache for Redis provides a centralized, external, and highly available session store that persists independently of EC2 instance lifecycles. This ensures that when instances are terminated or added during Auto Scaling events, session data remains intact and accessible from any instance, eliminating user logouts and data loss. It is operationally efficient as it requires minimal application code changes and leverages a fully managed, in-memory data store optimized for low-latency access.
What should I do if I get this SAP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is running a stateful web application on EC2 instances in an Auto Scaling group. Users report that their sessions are lost when instances are terminated during scale-in. What should a solutions architect do to preserve session state?
medium
A.Use lifecycle hooks to save session data to Amazon S3 before instance termination.
B.Enable sticky sessions (session affinity) on the Application Load Balancer.
✓ C.Store session state in Amazon ElastiCache.
D.Increase the Auto Scaling group's cooldown period to prevent rapid scaling.
Why C: Option D is correct because ElastiCache provides a centralized, fast session store that persists across instance terminations. Option A is wrong because sticky sessions (session affinity) can cause uneven load and still lose sessions if all instances in a target group are replaced. Option B is wrong because increasing cooldown delays scaling but does not prevent session loss. Option C is wrong because lifecycle hooks allow custom actions before termination, but moving session data during termination is complex and may not be reliable.
Last reviewed: Jun 11, 2026
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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.
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