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Resilient Cloud Solutions →hardMultiple ChoiceObjective-mapped

Quick Answer

The correct solution is to migrate ElastiCache for Redis to a cluster mode enabled configuration with multiple shards and enable Multi-AZ with automatic failover, along with read replicas in different AZs. This directly resolves the bottleneck because a single-node Redis instance with CPU above 80% cannot scale read traffic or provide failover, causing session state latency that elevates ALB TargetResponseTime. Cluster mode distributes the CPU load across shards, while Multi-AZ and read replicas deliver high availability and read scaling without any application code changes. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your ability to identify when a non-clustered Redis deployment is the root cause of performance degradation under peak load—a common trap is to over-focus on Auto Scaling or database tuning instead of the session store. Remember the memory tip: "Shard the load, spread the nodes, keep the session fast on peak roads."

DOP-C02 Resilient Cloud Solutions Practice Question

This DOP-C02 practice question tests your understanding of resilient cloud solutions. 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 production e-commerce platform on AWS. The architecture includes an Application Load Balancer (ALB) that distributes traffic to a fleet of Amazon EC2 instances running in an Auto Scaling group across three Availability Zones (AZs). The application stores session state in Amazon ElastiCache for Redis (cluster mode disabled) with a single node. The database is an Amazon Aurora MySQL DB cluster with one writer and two reader instances in different AZs. The platform experiences intermittent slowdowns and occasional timeouts during peak traffic hours. The CloudWatch metrics show that the ALB's TargetResponseTime is elevated, and the Redis CPU utilization is consistently above 80% during these periods. The Auto Scaling group is scaling out, but new instances take several minutes to become healthy. The DevOps team has been asked to improve the resilience and performance of the application with minimal changes to the application code. Which solution should the team implement?

Question 1hardmultiple 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 ElastiCache for Redis to a cluster mode enabled configuration with multiple shards and enable Multi-AZ with automatic failover. Also, use an ElastiCache replication group with read replicas in different AZs.

Option D is correct because the primary bottleneck is the single-node Redis instance (CPU > 80%), which cannot scale reads or handle failover. Migrating to cluster mode enabled with multiple shards distributes the CPU load across shards, while Multi-AZ with automatic failover and read replicas in different AZs provides high availability and read scaling. This directly addresses the elevated ALB TargetResponseTime caused by Redis latency without requiring application code changes.

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.

  • ✗

    Replace the ALB with a Network Load Balancer (NLB) to reduce latency, and use an Auto Scaling group with a step scaling policy based on Redis CPU utilization.

    Why it's wrong here

    NLB does not improve Redis performance; step scaling based on Redis CPU is not a standard metric and does not address the root cause.

  • ✗

    Increase the instance size of the ElastiCache for Redis node and the size of the Aurora writer instance. Also, increase the cooldown period for the Auto Scaling group to allow new instances to warm up.

    Why it's wrong here

    Vertical scaling is limited and does not eliminate the single point of failure; increasing cooldown may delay scaling response.

  • ✗

    Implement Amazon RDS Proxy in front of the Aurora cluster to reduce database connection overhead, and increase the size of the Redis instance to handle more connections.

    Why it's wrong here

    The bottleneck is Redis CPU, not database connections. RDS Proxy does not address Redis performance.

  • ✓

    Migrate ElastiCache for Redis to a cluster mode enabled configuration with multiple shards and enable Multi-AZ with automatic failover. Also, use an ElastiCache replication group with read replicas in different AZs.

    Why this is correct

    Cluster mode shards data, reducing per-node CPU. Multi-AZ and replicas improve resilience and reduce failover time.

    Related concept

    Read the scenario before looking for a memorised answer.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates focus on scaling the database or load balancer (options A, B, C) instead of recognizing that the single-node Redis cache is the bottleneck and requires horizontal scaling and high availability to resolve both performance and resilience issues.

Detailed technical explanation

How to think about this question

ElastiCache for Redis cluster mode enabled uses a sharded architecture where each shard handles a subset of keys, distributing CPU and memory load. Multi-AZ with automatic failover ensures that if the primary node fails, a read replica in another AZ is promoted, maintaining availability. The read replicas can serve read traffic, reducing load on the primary, which is critical when Redis CPU exceeds 80% and causes queuing delays that propagate to ALB target response times.

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 DOP-C02 question test?

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 ElastiCache for Redis to a cluster mode enabled configuration with multiple shards and enable Multi-AZ with automatic failover. Also, use an ElastiCache replication group with read replicas in different AZs. — Option D is correct because the primary bottleneck is the single-node Redis instance (CPU > 80%), which cannot scale reads or handle failover. Migrating to cluster mode enabled with multiple shards distributes the CPU load across shards, while Multi-AZ with automatic failover and read replicas in different AZs provides high availability and read scaling. This directly addresses the elevated ALB TargetResponseTime caused by Redis latency without requiring application code changes.

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.

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Last reviewed: Jun 11, 2026

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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.