The correct choice is migrating session state to ElastiCache for Redis, because it decouples session data from individual EC2 instances by externalizing session state for stateless architecture. This design change ensures that when instances are replaced during a deployment, the centralized Redis cluster persists all session data independently, preventing timeouts and errors that occur when in-memory caches are destroyed. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of stateless application patterns and the trade-offs between instance-local storage versus externalized state stores; a common trap is assuming sticky sessions or instance health checks alone solve the problem, but they do not survive instance termination. Remember the memory tip: “Redis lives on, even when EC2 is gone”—if your session state is externalized, your users won’t be logged out during rolling updates.
DOP-C02 Resilient Cloud Solutions Practice Question
This DOP-C02 practice question tests your understanding of resilient cloud solutions. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 EC2 instances behind an Application Load Balancer. The application stores session state in an in-memory cache on each instance. During deployment of a new version, users experience session timeouts and errors. Which design change will MOST effectively improve resilience and avoid session loss during deployments?
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 ElastiCache for Redis.
Option B is correct because migrating session state from in-memory EC2 instance storage to ElastiCache for Redis decouples session data from individual instances. This ensures that when a new deployment replaces instances, sessions persist independently, preventing timeouts and errors. ElastiCache provides a centralized, highly available session store that survives instance termination and scaling events.
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.
✗
Enable sticky sessions (session affinity) on the ALB.
Why it's wrong here
Stickiness alone does not preserve session data when the instance is replaced.
✓
Migrate session state to ElastiCache for Redis.
Why this is correct
Offloading session state to ElastiCache makes sessions durable across instance replacements.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the ALB idle timeout to 600 seconds.
Why it's wrong here
Idle timeout only affects connection persistence, not session data preservation.
✗
Increase the EC2 instance size to handle higher memory.
Why it's wrong here
Larger instances do not prevent session loss during deployments.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse sticky sessions (which only route traffic consistently) with session persistence (which requires external storage), leading them to choose option A despite it not preserving session data across instance replacements.
Detailed technical explanation
How to think about this question
ElastiCache for Redis stores session data as key-value pairs with built-in replication and automatic failover, ensuring durability across AZs. Under the hood, the application uses Redis commands like SETEX to store session data with a TTL, and the ALB distributes requests to any healthy instance, which retrieves the session from Redis. In a real-world scenario, a blue/green deployment with an external session store allows zero-downtime releases because new instances can immediately serve existing sessions without any warm-up or state migration.
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 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
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.
Resilient Cloud Solutions — This question tests Resilient Cloud Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Migrate session state to ElastiCache for Redis. — Option B is correct because migrating session state from in-memory EC2 instance storage to ElastiCache for Redis decouples session data from individual instances. This ensures that when a new deployment replaces instances, sessions persist independently, preventing timeouts and errors. ElastiCache provides a centralized, highly available session store that survives instance termination and scaling events.
What should I do if I get this DOP-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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company runs a critical web application on EC2 instances behind an Application Load Balancer (ALB). The application stores session state in an Amazon DynamoDB table. During a recent traffic spike, users experienced session timeouts and the application became unavailable. Which design change would BEST improve resilience?
medium
A.Move session state to Amazon ElastiCache for Redis with cluster mode disabled.
✓ B.Enable DynamoDB global tables or use a Multi-AZ deployment for the table.
C.Add a read replica to the DynamoDB table.
D.Increase the EC2 instance sizes to handle more traffic.
Why B: Option C is correct because using a Multi-AZ deployment for DynamoDB provides automatic failover and higher availability. Option A is wrong because increasing instance size does not address session state persistence. Option B is wrong because read replicas do not improve write availability. Option D is wrong because ElastiCache for Redis is not as resilient as DynamoDB Multi-AZ for session state.
Variation 2. A company runs a stateful web application on EC2 instances behind an ALB. The application stores session data in memory. The company wants to make the application stateless to improve resilience. Which TWO changes should the company make?
medium
A.Increase the instance memory to store more sessions
✓ B.Disable sticky sessions on the ALB
C.Enable sticky sessions (session affinity) on the ALB
✓ D.Store session data in Amazon ElastiCache for Redis
E.Use an NLB instead of an ALB
Why B: B and E are correct. Storing session data externally (ElastiCache) makes instances stateless. Enabling sticky sessions is not needed if state is external; however, the question asks for statelessness, so removing stickiness is correct. Option A is wrong because stickiness contradicts statelessness. Option C is wrong because in-memory storage is the problem. Option D is wrong because it doesn't address session state.
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This DOP-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 DOP-C02 exam.
Question Discussion
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