Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A developer is troubleshooting an AWS Lambda function that returns timeout errors when calling an external HTTPS API. The function is configured with a 30-second timeout and runs in a VPC with a public subnet and NAT Gateway. The developer checks CloudWatch logs and sees that the function is timing out at exactly 30 seconds. What is the most likely cause?
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
Distractor review
The NAT Gateway is not configured with a route to the internet.
The scenario states a NAT Gateway exists; lack of a route would cause a different failure, but the timeout at exactly the function timeout suggests a connection block rather than routing issue.
B
Best answer
The Lambda function's security group does not allow outbound traffic.
Correct. If the security group's outbound rules do not permit HTTPS traffic, the connection cannot be established, resulting in a timeout. This is the most common cause in such scenarios.
C
Distractor review
The external API's response time exceeds 30 seconds.
If the API response time were the issue, the function would likely hang until the timeout, but the function should have a sensible timeout. The pattern of exactly 30 seconds indicates the function timeout is being reached, not the API delay.
D
Distractor review
The Lambda function's VPC does not have an internet gateway.
In this scenario, the VPC has a NAT Gateway which requires an Internet Gateway. An Internet Gateway is present; the issue is not the IGW.
Common exam trap
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Technical deep dive
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
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?
CIDR notation defines the prefix length.
What is the correct answer to this question?
The correct answer is: The Lambda function's security group does not allow outbound traffic. — The Lambda function is in a VPC and needs outbound internet access via the NAT Gateway. If the function's security group does not allow outbound HTTPS traffic (port 443) to the internet, the connection attempt will be blocked, leading to a timeout after the function's configured timeout duration. The NAT Gateway is present, so the issue is likely a restrictive security group egress rule.
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.
Discussion
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