The answer is to enable sticky sessions on the Application Load Balancer using duration-based cookies. This is correct because ALB natively supports session stickiness by generating a specific cookie (AWSALB) that binds a user’s session to a particular target instance for the duration you define, ensuring subsequent requests from that client are routed to the same backend. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this concept tests your understanding of load balancer features versus other AWS services; a common trap is confusing ALB’s native cookie-based stickiness with Network Load Balancer (which lacks native session affinity) or assuming CloudFront or ElastiCache can handle this at the load balancer level. Remember, for session persistence at layer 7, always look for duration-based cookies on the ALB—think “ALB sticks with cookies, NLB just forwards packets.”
SAP-C02 Design for New Solutions Practice Question
This SAP-C02 practice question tests your understanding of design for new 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 is designing a new web application that will run on Amazon EC2 instances behind an Application Load Balancer (ALB). The application must support sticky sessions. What should they do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable sticky sessions on the ALB using duration-based cookies.
Option B is correct because ALB supports sticky sessions using cookies. Option A is wrong because NLB does not support sticky sessions natively. Option C is wrong because CloudFront does not handle session stickiness. Option D is wrong because ElastiCache is for caching, not session stickiness at the load balancer level.
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
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Configure an Amazon CloudFront distribution with session affinity.
Why it's wrong here
CloudFront session affinity is for edge caching, not for ALB.
✗
Store session data in Amazon ElastiCache and use a cookie to reference it.
Why it's wrong here
This is a possible solution but not a load balancer feature; the question asks what to do with the load balancer.
✓
Enable sticky sessions on the ALB using duration-based cookies.
Why this is correct
ALB supports sticky sessions via cookies.
Related concept
Static NAT maps one inside address to one outside address.
✗
Use a Network Load Balancer (NLB) with cross-zone load balancing.
Why it's wrong here
NLB does not support sticky sessions.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
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
How to think about this question
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.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
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
How this comes up in practice
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
Got this wrong? Here's your next step.
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 SAP-C02 NAT questions on configuration and troubleshooting.
Design for New Solutions — This question tests Design for New Solutions — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Enable sticky sessions on the ALB using duration-based cookies. — Option B is correct because ALB supports sticky sessions using cookies. Option A is wrong because NLB does not support sticky sessions natively. Option C is wrong because CloudFront does not handle session stickiness. Option D is wrong because ElastiCache is for caching, not session stickiness at the load balancer level.
What should I do if I get this SAP-C02 question wrong?
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 SAP-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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