Quick Answer
The answer is the Application Load Balancer with sticky sessions, also known as session stickiness. This is correct because sticky sessions, or session affinity, use a cookie (either application-generated or the ALB’s own AWSALB cookie) to bind a client’s entire session to a single healthy target, ensuring stateful application consistency even as traffic is distributed evenly across the fleet. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this concept tests your understanding of load balancing patterns for stateful workloads, often appearing in scenario-based questions where you must distinguish ALB sticky sessions from stateless alternatives like Network Load Balancers or Route53 weighted routing. A common trap is assuming NLB supports application-layer stickiness—it does not natively, as it operates at Layer 4. Remember the memory tip: “Sticky ALB cookies keep the session on the same box,” contrasting with NLB’s “no cookie, no stick.”
This DOP-C02 practice question tests your understanding of resilient cloud solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 stateful application on EC2 instances. They want to distribute traffic evenly and maintain session stickiness. Which AWS service should they use?
Network Load Balancer
Why wrong: NLB does not support application-level stickiness.
Application Load Balancer with sticky sessions
ALB supports sticky sessions via cookies.
Amazon Route 53 weighted routing policy
Why wrong: Route53 does not provide stickiness.
Amazon CloudFront with origin failover
Why wrong: CloudFront is a CDN, not a load balancer.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Application Load Balancer with sticky sessions
An Application Load Balancer with sticky sessions (session affinity) ensures that a client's requests are sent to the same target. Option A is wrong because Network Load Balancer does not natively support sticky sessions based on application cookies. Option C is wrong because Route53 weighted routing does not handle session stickiness. Option D is wrong because CloudFront can forward cookies but is not primarily for load balancing.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Network Load Balancer
Why it's wrong here
NLB does not support application-level stickiness.
Application Load Balancer with sticky sessions
Why this is correct
ALB supports sticky sessions via cookies.
Related concept
Static NAT maps one inside address to one outside address.
Amazon Route 53 weighted routing policy
Why it's wrong here
Route53 does not provide stickiness.
Amazon CloudFront with origin failover
Why it's wrong here
CloudFront is a CDN, not a load balancer.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
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FAQ
Resilient Cloud Solutions — This question tests Resilient Cloud Solutions — Static NAT maps one inside address to one outside address..
The correct answer is: Application Load Balancer with sticky sessions — An Application Load Balancer with sticky sessions (session affinity) ensures that a client's requests are sent to the same target. Option A is wrong because Network Load Balancer does not natively support sticky sessions based on application cookies. Option C is wrong because Route53 weighted routing does not handle session stickiness. Option D is wrong because CloudFront can forward cookies but is not primarily for load balancing.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 20, 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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