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Reliability and Business Continuity →mediumMultiple ChoiceObjective-mapped

Quick Answer

The correct answer is to migrate session state to Amazon ElastiCache for Redis, store critical data in Amazon EFS, deploy an Auto Scaling group across multiple Availability Zones, and place it behind an Application Load Balancer. This combination works because it decouples the application’s state from individual EC2 instances: ElastiCache provides a centralized, in-memory session store that any instance can access, while Amazon EFS offers a shared, NFS-based file system that persists critical data across AZs—unlike EBS, which is tied to a single zone. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of the stateless architecture pattern required for high availability; a common trap is assuming EBS Multi-Attach or a simple EBS snapshot strategy can survive an AZ failure, but EBS cannot be shared across AZs. Remember the memory tip: “State in cache, data in file share, spread across zones” to quickly recall that ElastiCache handles session state, EFS handles persistent files, and multi-AZ Auto Scaling handles fault tolerance.

SOA-C02 Reliability and Business Continuity Practice Question

This SOA-C02 practice question tests your understanding of reliability and business continuity. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: amazon ElastiCache for Redis provides a managed, in-memory data store for session state.. 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 a single Amazon EC2 instance. The SysOps administrator needs to implement a high availability architecture that can tolerate an Availability Zone (AZ) failure. The application stores session state in memory and also writes critical data to an Amazon EBS volume. The administrator wants to use an Auto Scaling group and an Application Load Balancer (ALB). Which combination of steps is required to make the application highly available?

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

✓

Migrate session state to Amazon ElastiCache for Redis, store critical data in Amazon EFS, create an Auto Scaling group across multiple AZs, and place it behind an ALB.

Option B is correct because it addresses both the stateless requirement for horizontal scaling and the persistence of critical data across AZ failures. Migrating session state to ElastiCache for Redis removes the dependency on local instance memory, allowing any instance to handle any request. Storing critical data on Amazon EFS provides a shared, NFS-based file system that is accessible from all instances across multiple AZs, unlike EBS which is tied to a single AZ. Combining these with a multi-AZ Auto Scaling group and an ALB ensures the application can survive an entire AZ outage.

Key principle: Amazon ElastiCache for Redis provides a managed, in-memory data store for session state.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✗

    Create an Auto Scaling group that spans at least two Availability Zones, attach the existing EBS volume to the new instances, and use an ALB to distribute traffic.

    Why it's wrong here

    An EBS volume can only be attached to one instance at a time. To share data, use a distributed file system like Amazon EFS or a database. This option does not solve the stateful issue.

  • ✓

    Migrate session state to Amazon ElastiCache for Redis, store critical data in Amazon EFS, create an Auto Scaling group across multiple AZs, and place it behind an ALB.

    Why this is correct

    Externalizing session state and data to shared services (ElastiCache, EFS) allows any instance to take over. An Auto Scaling group across multiple AZs and an ALB provide fault tolerance for AZ failures.

    Related concept

    Amazon ElastiCache for Redis provides a managed, in-memory data store for session state.

  • ✗

    Place the EC2 instance in an Auto Scaling group with a minimum and maximum of 1 in the same AZ, and attach an Elastic IP to the instance.

    Why it's wrong here

    This does not provide multi-AZ redundancy. An AZ failure would still cause an outage. An Elastic IP does not provide automatic failover.

  • ✗

    Use an ALB with the existing single instance as the target, and enable cross-zone load balancing.

    Why it's wrong here

    A single instance cannot survive an AZ failure if the AZ fails. Cross-zone load balancing distributes traffic across instances in different AZs, but there is only one instance in one AZ.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates assume EBS volumes can be shared across instances or AZs, or that a single-instance setup with an ALB provides high availability, when in fact EBS is a single-AZ resource and the ALB requires multiple healthy targets to tolerate failures.

Detailed technical explanation

How to think about this question

Under the hood, ElastiCache for Redis uses a replication group with automatic failover across AZs, ensuring session data is durable even if a cache node fails. Amazon EFS uses a standard NFSv4.1 protocol and is designed to be accessible from all AZs in a region simultaneously, with data stored redundantly across multiple AZs. The Auto Scaling group's health check integration with the ALB ensures that unhealthy instances are terminated and replaced, while the ALB's cross-zone load balancing (enabled by default) distributes traffic evenly across all healthy instances in all AZs.

KKey Concepts to Remember

  • Amazon ElastiCache for Redis provides a managed, in-memory data store for session state.
  • Amazon EFS is a scalable, shared file system mountable by multiple EC2 instances across AZs.
  • Auto Scaling groups automatically replace unhealthy instances and scale across AZs.
  • Application Load Balancers distribute traffic to instances in multiple Availability Zones.

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

Amazon ElastiCache for Redis provides a managed, in-memory data store for session state.

Real-world example

How this comes up in practice

A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.

What to study next

Got this wrong? Here's your next step.

Review amazon ElastiCache for Redis provides a managed, in-memory data store for session state., then practise related SOA-C02 questions on the same topic to reinforce the concept.

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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 — Amazon ElastiCache for Redis provides a managed, in-memory data store for session state..

What is the correct answer to this question?

The correct answer is: Migrate session state to Amazon ElastiCache for Redis, store critical data in Amazon EFS, create an Auto Scaling group across multiple AZs, and place it behind an ALB. — Option B is correct because it addresses both the stateless requirement for horizontal scaling and the persistence of critical data across AZ failures. Migrating session state to ElastiCache for Redis removes the dependency on local instance memory, allowing any instance to handle any request. Storing critical data on Amazon EFS provides a shared, NFS-based file system that is accessible from all instances across multiple AZs, unlike EBS which is tied to a single AZ. Combining these with a multi-AZ Auto Scaling group and an ALB ensures the application can survive an entire AZ outage.

What should I do if I get this SOA-C02 question wrong?

Review amazon ElastiCache for Redis provides a managed, in-memory data store for session state., then practise related SOA-C02 questions on the same topic to reinforce the concept.

What is the key concept behind this question?

Amazon ElastiCache for Redis provides a managed, in-memory data store for session state.

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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.