- A
Use an SQS FIFO queue between Kinesis and Lambda.
Why wrong: Kinesis cannot directly send to SQS.
- B
Use a DynamoDB table to store processed record IDs and perform deduplication in the Lambda function.
This provides exactly-once semantics.
- C
Enable Lambda reserved concurrency to limit retries.
Why wrong: Reserved concurrency does not prevent duplicates.
- D
Reduce the batch size in the event source mapping.
Why wrong: Smaller batches do not eliminate duplicates from retries.
Question 754 of 1,616
Exactly-Once Processing with Lambda and Kinesis
This DVA-C02 practice question tests your understanding of development with aws services. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 critical application on AWS Lambda that processes real-time data from Kinesis Data Streams. The function is idempotent, but occasionally duplicate records are processed due to retries. The company wants to ensure exactly-once processing. Which approach should the developer implement?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a DynamoDB table to store processed record IDs and perform deduplication in the Lambda function.
Option B is correct because DynamoDB provides a scalable, low-latency store for tracking processed record IDs, enabling the Lambda function to check for duplicates before processing. Since the function is idempotent but retries cause duplicates, a DynamoDB-based deduplication layer ensures exactly-once semantics without altering the event source or introducing ordering constraints.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use an SQS FIFO queue between Kinesis and Lambda.
Why it's wrong here
Kinesis cannot directly send to SQS.
- ✓
Use a DynamoDB table to store processed record IDs and perform deduplication in the Lambda function.
Why this is correct
This provides exactly-once semantics.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Enable Lambda reserved concurrency to limit retries.
Why it's wrong here
Reserved concurrency does not prevent duplicates.
- ✗
Reduce the batch size in the event source mapping.
Why it's wrong here
Smaller batches do not eliminate duplicates from retries.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume SQS FIFO queues guarantee exactly-once processing end-to-end, but they overlook that Kinesis itself does not provide exactly-once delivery, so duplicates can still originate from the stream before reaching the queue.
Detailed technical explanation
How to think about this question
Under the hood, Kinesis Data Streams uses an at-least-once delivery model, meaning the same record can be delivered multiple times during retries or shard rebalancing. DynamoDB conditional writes (e.g., `ConditionExpression: attribute_not_exists(RecordId)`) provide atomic deduplication, ensuring only the first write succeeds. In real-world scenarios, you must also handle TTL-based cleanup to avoid unbounded table growth, and consider using a composite key (e.g., shard ID + sequence number) for uniqueness.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this DVA-C02 question test?
Development with AWS Services — This question tests Development with AWS Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a DynamoDB table to store processed record IDs and perform deduplication in the Lambda function. — Option B is correct because DynamoDB provides a scalable, low-latency store for tracking processed record IDs, enabling the Lambda function to check for duplicates before processing. Since the function is idempotent but retries cause duplicates, a DynamoDB-based deduplication layer ensures exactly-once semantics without altering the event source or introducing ordering constraints.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This DVA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DVA-C02 exam.
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