- A
Increase the cooldown period for the Auto Scaling group.
Why wrong: Cooldown delays scaling but does not preserve sessions across terminated instances.
- B
Modify the application to store session data in an external data store such as ElastiCache or DynamoDB.
Why wrong: This is an effective long-term solution but requires application changes; the question asks for the most effective solution among the options.
- C
Enable sticky sessions (session affinity) on the Application Load Balancer.
Sticky sessions route a user's requests to the same instance, preserving sessions during scaling if the instance is not terminated.
- D
Use larger EC2 instance types to reduce the frequency of scaling.
Why wrong: Larger instances reduce scaling events but do not guarantee session persistence when scaling does occur.
SOA-C02 Reliability and Business Continuity Practice Question
This SOA-C02 practice question tests your understanding of reliability and business continuity. 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 behind an Application Load Balancer. Users report that their sessions are frequently lost during scaling events. What is the MOST effective solution to maintain session persistence?
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
Enable sticky sessions (session affinity) on the Application Load Balancer.
Option D is correct because enabling sticky sessions (session affinity) on the ALB ensures that a user's requests are routed to the same instance during a session. Option A is wrong because increasing the cooldown delay does not solve session loss during scale-in. Option B is wrong while helpful for state offloading, it does not address the immediate issue of session persistence; a full rewrite may be needed. Option C is wrong because a larger instance size does not prevent session loss when instances are terminated.
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
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the cooldown period for the Auto Scaling group.
Why it's wrong here
Cooldown delays scaling but does not preserve sessions across terminated instances.
- ✗
Modify the application to store session data in an external data store such as ElastiCache or DynamoDB.
Why it's wrong here
This is an effective long-term solution but requires application changes; the question asks for the most effective solution among the options.
- ✓
Enable sticky sessions (session affinity) on the Application Load Balancer.
Why this is correct
Sticky sessions route a user's requests to the same instance, preserving sessions during scaling if the instance is not terminated.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Use larger EC2 instance types to reduce the frequency of scaling.
Why it's wrong here
Larger instances reduce scaling events but do not guarantee session persistence when scaling does occur.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
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
How to think about this question
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.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
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
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
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.
- →
Reliability and Business Continuity — study guide chapter
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FAQ
Questions learners often ask
What does this SOA-C02 question test?
Reliability and Business Continuity — This question tests Reliability and Business Continuity — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Enable sticky sessions (session affinity) on the Application Load Balancer. — Option D is correct because enabling sticky sessions (session affinity) on the ALB ensures that a user's requests are routed to the same instance during a session. Option A is wrong because increasing the cooldown delay does not solve session loss during scale-in. Option B is wrong while helpful for state offloading, it does not address the immediate issue of session persistence; a full rewrite may be needed. Option C is wrong because a larger instance size does not prevent session loss when instances are terminated.
What should I do if I get this SOA-C02 question wrong?
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.
What is the key concept behind this question?
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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