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Reliability and Business Continuity →mediumMultiple ChoiceObjective-mapped

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 critical web application on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer (ALB). The application uses session stickiness (sticky sessions) to maintain user sessions. The SysOps administrator notices that when instances are replaced during a scale-in or failure event, users lose their session data. The administrator needs to preserve session data across instance failures without losing stickiness benefits. What should the administrator do?

Question 1mediummultiple choice
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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

✓

Disable sticky sessions on the ALB and configure the application to store session data in an external session store like Amazon ElastiCache for Redis.

Option A is correct because storing session data externally in a service like Amazon ElastiCache for Redis decouples session state from the EC2 instance lifecycle. This allows the ALB to continue using sticky sessions to route a user to the same instance, but if that instance fails or is replaced, the new instance can retrieve the session data from the shared Redis cache, preserving the user's session without interruption.

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.

  • ✓

    Disable sticky sessions on the ALB and configure the application to store session data in an external session store like Amazon ElastiCache for Redis.

    Why this is correct

    This decouples session state from the EC2 instance. If an instance fails, any other instance can retrieve the session from ElastiCache, preserving the session for the user.

    Related concept

    Read the scenario before looking for a memorised answer.

  • ✗

    Increase the stickiness duration to a very high value so that sessions are not lost during brief interruptions.

    Why it's wrong here

    Stickiness only controls how long the load balancer binds a user to an instance. If the instance fails, the session is lost regardless of the duration.

  • ✗

    Change the Auto Scaling group to use a larger instance type to handle more sessions per instance, reducing the likelihood of session loss.

    Why it's wrong here

    This does not prevent data loss if an instance fails. Sessions are still stored locally on the instance.

  • ✗

    Configure the Auto Scaling group to use a larger minimum size and a lower maximum, so instances are less likely to be terminated.

    Why it's wrong here

    While this reduces the frequency of scale-in events, it does not protect against instance failures. Sessions are still lost on instance termination.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates may think sticky sessions alone preserve session data, but they only preserve routing affinity, not the session state itself, which must be stored externally to survive instance failures.

Detailed technical explanation

How to think about this question

Under the hood, ALB sticky sessions work by setting a cookie (AWSALB or AWSALBCORS) that maps a user to a specific target instance. However, the ALB does not replicate or persist session data; it only routes traffic. By using ElastiCache for Redis as an external session store, the application writes session data to Redis, which is highly available and durable. When an instance fails, the new instance reads the session from Redis, and the ALB's sticky cookie still routes the user to the same instance (or a new one if the original is gone), ensuring seamless continuity. This pattern is often called 'stateless application with stateful session store' and is a best practice for high-availability web applications.

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

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.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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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 — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Disable sticky sessions on the ALB and configure the application to store session data in an external session store like Amazon ElastiCache for Redis. — Option A is correct because storing session data externally in a service like Amazon ElastiCache for Redis decouples session state from the EC2 instance lifecycle. This allows the ALB to continue using sticky sessions to route a user to the same instance, but if that instance fails or is replaced, the new instance can retrieve the session data from the shared Redis cache, preserving the user's session without interruption.

What should I do if I get this SOA-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.

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Last reviewed: Jun 11, 2026

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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.