Quick Answer
The correct answer is to use Amazon ElastiCache for Redis to store session data externally. This solution works because it decouples session state from the individual EC2 instance, making the application stateless and allowing any instance in the Auto Scaling group to handle requests without relying on local storage. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of how to migrate a legacy application to Auto Scaling with an external session store while minimizing code changes—a common trap is assuming sticky sessions (session affinity) are sufficient, but they still leave sessions vulnerable to instance failure. The key insight is that ElastiCache for Redis provides a centralized, in-memory data store that the application can access without rewriting core logic, as long as it supports Redis configuration. Remember the mnemonic: “Redis Removes Reliance on Local Storage” to recall that externalizing session data is the cleanest path to a scalable, fault-tolerant architecture.
This SOA-C02 practice question tests your understanding of deployment, provisioning, and automation. 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 has a legacy application that runs on a single Amazon EC2 instance. The SysOps administrator is tasked with migrating the application to an Auto Scaling group behind an Application Load Balancer to improve availability. The application stores session state locally on the instance. What should the administrator do to ensure a seamless migration with minimal changes to the application code?
Configure the Application Load Balancer with sticky sessions (session affinity).
Why wrong: Why A is wrong
Disable the feature that stores session state locally.
Why wrong: Why D is wrong
Use Amazon ElastiCache for Redis to store session data externally.
Why B is correct
Modify the application to store session data in an Amazon RDS database.
Why wrong: Why C is wrong
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use Amazon ElastiCache for Redis to store session data externally.
Option B is correct because ElastiCache for Redis provides a centralized session store that can be accessed by any instance, allowing the application to be stateless without code changes if the application is configured to use Redis. Option A is incorrect because Sticky Sessions (session affinity) is a workaround but does not eliminate the dependency on local storage; if an instance fails, sessions are lost. Option C is incorrect because modifying the application to use a database for session storage requires code changes. Option D is incorrect because disabling the feature does not solve the problem.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Configure the Application Load Balancer with sticky sessions (session affinity).
Why it's wrong here
Why A is wrong
Disable the feature that stores session state locally.
Why it's wrong here
Why D is wrong
Use Amazon ElastiCache for Redis to store session data externally.
Why this is correct
Why B is correct
Related concept
Static NAT maps one inside address to one outside address.
Modify the application to store session data in an Amazon RDS database.
Why it's wrong here
Why C is wrong
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
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
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SOA-C02 NAT questions on configuration and troubleshooting.
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FAQ
Deployment, Provisioning, and Automation — This question tests Deployment, Provisioning, and Automation — Static NAT maps one inside address to one outside address..
The correct answer is: Use Amazon ElastiCache for Redis to store session data externally. — Option B is correct because ElastiCache for Redis provides a centralized session store that can be accessed by any instance, allowing the application to be stateless without code changes if the application is configured to use Redis. Option A is incorrect because Sticky Sessions (session affinity) is a workaround but does not eliminate the dependency on local storage; if an instance fails, sessions are lost. Option C is incorrect because modifying the application to use a database for session storage requires code changes. Option D is incorrect because disabling the feature does not solve the problem.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SOA-C02 NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 20, 2026
This SOA-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 SOA-C02 exam.
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