The answer is to enable sticky sessions on the Application Load Balancer. This is correct because sticky sessions, also known as session affinity, force the ALB to route a user’s requests to the same EC2 instance throughout their session, preserving the state data written to local instance store. Since the application stores state on ephemeral instance storage, any scaling event that terminates an instance would otherwise destroy that local data; sticky sessions prevent users from being redirected to a new instance mid-session. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how to handle stateful applications without modifying code—a common trap is to suggest larger instances or EBS volumes, but those don’t solve the routing problem. Remember the memory tip: “Stick to the same instance to keep state persistent.”
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 stateful application on EC2 instances in an Auto Scaling group. The application stores state on local instance storage. During a scaling event, users lose session data. How can the company make the application resilient without modifying the application code?
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 Application Load Balancer.
Option D is correct because using a sticky session (session affinity) on the ALB ensures users are routed to the same instance, preserving local state. Option A is wrong because larger instances do not prevent data loss on termination. Option B is wrong because EBS volumes persist but require reattachment. Option C is wrong because reducing cooldown does not preserve state.
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.
✗
Reduce the Auto Scaling group cooldown period.
Why it's wrong here
Cooldown does not preserve state.
✓
Enable sticky sessions on the Application Load Balancer.
Why this is correct
Sticky sessions route users to the same instance, preserving local state.
Related concept
Static NAT maps one inside address to one outside address.
✗
Increase the instance size to reduce scaling events.
Why it's wrong here
Scaling events can still occur, and state is still lost on instance termination.
✗
Use Elastic Block Store (EBS) volumes instead of instance store.
Why it's wrong here
EBS volumes persist but still need to be reattached to new instances, which requires application changes.
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 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.
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.
Resilient Cloud Solutions — This question tests Resilient Cloud 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 Application Load Balancer. — Option D is correct because using a sticky session (session affinity) on the ALB ensures users are routed to the same instance, preserving local state. Option A is wrong because larger instances do not prevent data loss on termination. Option B is wrong because EBS volumes persist but require reattachment. Option C is wrong because reducing cooldown does not preserve state.
What should I do if I get this DOP-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 DOP-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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