Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A developer is building a serverless application that uses Amazon S3 event notifications to trigger an AWS Lambda function for thumbnail generation. The developer wants to ensure that duplicate S3 events do not cause the same image to be processed multiple times. Which approach should the developer implement to ensure idempotent processing?
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
Store the object key and event ID in a DynamoDB table and check for duplicates before processing
By recording processed object keys in DynamoDB and checking for existing records, the function can skip duplicate events, ensuring each object is processed only once.
B
Distractor review
Set the Lambda function's concurrency to 1 to prevent concurrent executions
Limiting concurrency does not prevent duplicate events; it only ensures that only one invocation runs at a time, but duplicate events can still arrive and be processed sequentially.
C
Distractor review
Use an Amazon SQS FIFO queue as the event destination
S3 event notifications cannot be sent to FIFO queues; only standard queues are supported.
D
Distractor review
Enable S3 event notification filtering based on object size
Filtering based on object size controls which objects trigger events, but does not prevent duplicates for objects that match the filter.
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: Store the object key and event ID in a DynamoDB table and check for duplicates before processing — S3 event notifications are delivered on an at-least-once basis, meaning duplicate events can occur. To achieve idempotent processing, the Lambda function should track which objects have already been processed, typically by storing the object key or a unique event identifier in a DynamoDB table. On each invocation, the function can check the table and skip processing if the record exists. Setting concurrency to 1 does not prevent duplicate events, S3 cannot send notifications to FIFO queues, and filtering on object size does not eliminate duplicates.
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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