- A
Change the scaling policy to a simple scaling policy instead of dynamic scaling
Why wrong: Simple scaling does not prevent session loss; the core issue is that session state is stored in memory on the instance.
- B
Enable sticky sessions (session affinity) on the Application Load Balancer
Why wrong: Stickiness routes users to the same instance, but if that instance is terminated due to scaling in, the session is still lost.
- C
Modify the application to store session state in an Amazon ElastiCache cluster
ElastiCache provides a centralized session store that persists across instance terminations, ensuring session continuity during scaling events.
- D
Increase the cooldown period for the Auto Scaling group
Why wrong: Cooldown period only affects when new scaling activities can start; it does not preserve session data.
Quick Answer
The correct answer is to modify the application to store session state in an Amazon ElastiCache cluster. This resolves the issue because externalizing session state with ElastiCache for scaling decouples the session data from the individual EC2 instances, so when the Auto Scaling group terminates or launches instances based on CPU utilization, users are not logged out or lose their data—any instance can serve any request by reading the shared, in-memory cache. On the AWS Certified SAP on AWS Specialty PAS-C01 exam, this scenario tests your understanding of stateful application patterns and the need to offload session persistence to a dedicated service like ElastiCache rather than relying on sticky sessions or instance-local storage. A common trap is assuming that enabling sticky sessions (Session Affinity) on the load balancer alone will fix the issue, but that only routes traffic to the same instance during its lifetime—it does not preserve state when that instance is terminated during a scale-in event. Memory tip: think “Cache the state, not the instance”—ElastiCache keeps sessions alive even when instances come and go.
PAS-C01 Technology Practice Question
This PAS-C01 practice question tests your understanding of technology. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 runs a stateful web application on EC2 instances in an Auto Scaling group with a dynamic scaling policy based on CPU utilization. The application maintains session state in memory on each instance. Users report that they are frequently logged out and lose their session data during scaling events. What should the company do to resolve this issue?
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
Modify the application to store session state in an Amazon ElastiCache cluster
Option C is correct because storing session state externally in ElastiCache decouples session data from individual EC2 instances. This ensures that when instances are terminated or added during scaling events, users retain their session state regardless of which instance serves their request. ElastiCache provides a low-latency, in-memory cache that is ideal for session persistence in stateful web applications.
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.
- ✗
Change the scaling policy to a simple scaling policy instead of dynamic scaling
Why it's wrong here
Simple scaling does not prevent session loss; the core issue is that session state is stored in memory on the instance.
- ✗
Enable sticky sessions (session affinity) on the Application Load Balancer
Why it's wrong here
Stickiness routes users to the same instance, but if that instance is terminated due to scaling in, the session is still lost.
- ✓
Modify the application to store session state in an Amazon ElastiCache cluster
Why this is correct
ElastiCache provides a centralized session store that persists across instance terminations, ensuring session continuity during scaling events.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Increase the cooldown period for the Auto Scaling group
Why it's wrong here
Cooldown period only affects when new scaling activities can start; it does not preserve session data.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse sticky sessions (session affinity) with true session persistence, not realizing that sticky sessions only route traffic to the same instance but do not protect against instance termination during scaling events.
Detailed technical explanation
How to think about this question
Under the hood, ElastiCache for Redis or Memcached provides a distributed, highly available key-value store that can be accessed by any EC2 instance via standard protocols (e.g., Redis RESP). By storing session tokens and data in ElastiCache, the application can retrieve session state from any instance, making the architecture stateless from the instance perspective. In real-world scenarios, this pattern is critical for Auto Scaling groups with dynamic policies, as it allows safe scale-in without requiring instance termination protection or complex lifecycle hooks.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
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FAQ
Questions learners often ask
What does this PAS-C01 question test?
Technology — This question tests Technology — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Modify the application to store session state in an Amazon ElastiCache cluster — Option C is correct because storing session state externally in ElastiCache decouples session data from individual EC2 instances. This ensures that when instances are terminated or added during scaling events, users retain their session state regardless of which instance serves their request. ElastiCache provides a low-latency, in-memory cache that is ideal for session persistence in stateful web applications.
What should I do if I get this PAS-C01 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.
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Last reviewed: Jun 11, 2026
This PAS-C01 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 PAS-C01 exam.
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