Question 1easymultiple choice
Full question →easymultiple choiceObjective-mapped
An application running on Amazon EC2 instances behind an Application Load Balancer (ALB) intermittently returns 503 errors. The ALB health checks are failing for some instances intermittently. The developer checks the instance system logs and finds no application errors. What is the most likely cause of the health check failures?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
The application on the instances is experiencing resource exhaustion (e.g., memory or CPU) which causes it to stop responding to health checks temporarily
Intermittent failures suggest transient issues like high resource utilization. The application may become unresponsive during spikes, causing health checks to fail until resources are freed.
B
Distractor review
The security group for the instances does not allow inbound traffic from the ALB on the health check port
Security group misconfiguration would cause health checks to fail consistently, not intermittently.
C
Distractor review
The health check path is not configured correctly and the default path returns a 404 status
Incorrect health check configuration would result in persistent failures for all instances.
D
Distractor review
The target group is not configured with the correct protocol
Protocol mismatch would cause consistent health check failures.
Common exam trap
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.
Technical deep dive
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.
Related practice questions
Related DVA-C02 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A developer is building a REST API using Amazon API Gateway that will serve static content from an Amazon S3 bucket. The API should cache responses for frequently accessed objects to reduce latency. Which API Gateway feature should the developer enable?
Question 2
A developer is running a web application on multiple Amazon EC2 instances behind an Application Load Balancer (ALB). The application needs to store user session state that must be available across all instances. The session data is small and temporary but must survive individual instance failures. Which AWS service should the developer use to store this session state?
Question 3
A developer has an AWS Lambda function that processes messages from an Amazon SQS standard queue. The function is idempotent and currently has a batch size of 10. The developer wants to increase throughput and increases the batch size to 100. After the change, CloudWatch metrics show a significant increase in throttles and the queue backlog is growing. The function's reserved concurrency is set to 10. What is the most effective action to resolve the throttling and improve throughput?
Question 4
A developer is managing an application running on Amazon EC2 instances behind an Application Load Balancer. Users report that the application becomes unresponsive after several hours, and restarting the instance temporarily fixes the issue. The developer suspects a memory leak but cannot add custom instrumentation. Which AWS service can collect memory utilization metrics and help identify the memory leak with minimal configuration?
Question 5
A developer is building a serverless web application using AWS Lambda and Amazon DynamoDB. The application needs to perform complex aggregations on data stored in DynamoDB. Which AWS service should the developer use to perform these aggregations efficiently without reading all the data into Lambda?
Question 6
A developer has an Amazon S3 bucket containing private user documents. The application must generate a time-limited URL for users to download their own documents without requiring the users to have AWS credentials. Which solution should the developer use?
FAQ
Questions learners often ask
What does this DVA-C02 question test?
Static NAT maps one inside address to one outside address.
What is the correct answer to this question?
The correct answer is: The application on the instances is experiencing resource exhaustion (e.g., memory or CPU) which causes it to stop responding to health checks temporarily — Intermittent health check failures without application error logs typically indicate transient resource exhaustion, such as memory or CPU spikes, that cause the application to stop responding to health checks temporarily. The health check path may become unresponsive when the instance is under heavy load. Security group issues or incorrect health check configuration would cause consistent failures, not intermittent. Resource exhaustion may not be directly logged in application system logs.
What should I do if I get this DVA-C02 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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