- A
Configure the ALB with cross-zone load balancing enabled and connection draining set to a suitable timeout.
Cross-zone load balancing distributes traffic evenly, and connection draining allows in-flight requests to complete during instance replacement.
- B
Deploy an Auto Scaling group with a dynamic scaling policy that adds instances in the remaining AZs.
Why wrong: Auto Scaling helps with capacity but does not preserve session state; session data loss would still occur.
- C
Enable cluster mode for the ElastiCache for Redis cluster and configure replica nodes in different Availability Zones.
Cluster mode with replicas across AZs provides data redundancy and high availability.
- D
Configure the application to use a custom DNS name with a low TTL pointing to the ElastiCache cluster endpoint.
Why wrong: DNS TTL does not impact session state; it helps with failover but does not prevent data loss.
- E
Enable Multi-AZ for the ElastiCache cluster to automatically fail over to a replica in another AZ.
Why wrong: ElastiCache for Redis does not support Multi-AZ; it supports cluster mode with replica nodes in different AZs.
Quick Answer
The answer is to enable cluster mode for the ElastiCache for Redis cluster and configure replica nodes in different Availability Zones. This configuration ensures session state persistence across AZ failures by automatically sharding data across multiple primary nodes and replicating each shard’s data to a replica in a separate AZ, so if a primary node in one AZ goes down, a replica in another AZ can be promoted without losing session data. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this question tests your understanding of Redis replication and AZ-aware architecture, often appearing as a trap where candidates mistakenly focus on ALB settings like cross-zone load balancing or connection draining, which handle traffic distribution but do not protect the session store itself. The key insight is that ElastiCache cluster mode with multi-AZ replicas provides the data-plane resilience needed to survive an AZ outage. Memory tip: “Cluster mode for cache, not just for compute—replicate across AZs to keep sessions safe.”
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 critical web application on Amazon EC2 instances behind an Application Load Balancer (ALB) across multiple Availability Zones. The application stores session data in a shared Amazon ElastiCache for Redis cluster. The operations team reports that during a recent AZ failure, users experienced session loss and application errors. Which combination of actions should the company take to improve resilience and maintain session state during an AZ failure? (Choose TWO.)
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
Configure the ALB with cross-zone load balancing enabled and connection draining set to a suitable timeout.
Option A is correct because enabling cross-zone load balancing on the ALB ensures traffic is distributed evenly across all EC2 instances in all AZs, and connection draining with a suitable timeout allows in-flight requests to complete before instances are deregistered, preventing session loss during an AZ failure. Option C is correct because enabling cluster mode for ElastiCache for Redis with replica nodes in different AZs provides automatic sharding and replication, ensuring session data remains available and consistent even if a primary node in one AZ fails.
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.
- ✓
Configure the ALB with cross-zone load balancing enabled and connection draining set to a suitable timeout.
Why this is correct
Cross-zone load balancing distributes traffic evenly, and connection draining allows in-flight requests to complete during instance replacement.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Deploy an Auto Scaling group with a dynamic scaling policy that adds instances in the remaining AZs.
Why it's wrong here
Auto Scaling helps with capacity but does not preserve session state; session data loss would still occur.
- ✓
Enable cluster mode for the ElastiCache for Redis cluster and configure replica nodes in different Availability Zones.
Why this is correct
Cluster mode with replicas across AZs provides data redundancy and high availability.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Configure the application to use a custom DNS name with a low TTL pointing to the ElastiCache cluster endpoint.
Why it's wrong here
DNS TTL does not impact session state; it helps with failover but does not prevent data loss.
- ✗
Enable Multi-AZ for the ElastiCache cluster to automatically fail over to a replica in another AZ.
Why it's wrong here
ElastiCache for Redis does not support Multi-AZ; it supports cluster mode with replica nodes in different AZs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Multi-AZ (which provides a single standby replica) with cluster mode (which provides sharded, distributed replication across AZs), and fail to recognize that Multi-AZ alone does not protect session data if the primary and replica are in the same AZ or if the failure affects the entire AZ containing both nodes.
Detailed technical explanation
How to think about this question
Under the hood, ALB connection draining works by setting a deregistration delay (default 300 seconds) that allows the load balancer to stop sending new requests to draining instances while completing existing connections, using the TCP FIN or HTTP keep-alive timeout. For ElastiCache Redis cluster mode, data is partitioned across up to 500 shards, each with a primary and up to 5 replicas; during an AZ failure, Redis automatically promotes a replica in a healthy AZ to primary for each affected shard, using the Redis Cluster protocol (gossip-based) to maintain quorum and avoid split-brain scenarios.
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: Configure the ALB with cross-zone load balancing enabled and connection draining set to a suitable timeout. — Option A is correct because enabling cross-zone load balancing on the ALB ensures traffic is distributed evenly across all EC2 instances in all AZs, and connection draining with a suitable timeout allows in-flight requests to complete before instances are deregistered, preventing session loss during an AZ failure. Option C is correct because enabling cluster mode for ElastiCache for Redis with replica nodes in different AZs provides automatic sharding and replication, ensuring session data remains available and consistent even if a primary node in one AZ fails.
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
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Last reviewed: Jun 11, 2026
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.
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