- A
The Kinesis data stream's retention period is too long, causing old records to be reprocessed.
Why wrong: Retention period does not cause reprocessing.
- B
The function's reserved concurrency is set too low, causing invocations to be throttled and retried.
Why wrong: Throttled invocations are not retried automatically for Kinesis.
- C
The batch size is set too high, causing the function to process records in multiple batches.
Why wrong: Batch size affects batch processing, not duplicate processing.
- D
The Kinesis stream's iterator age is too low, causing the function to reprocess records after a failure.
Low iterator age means the function may fall behind and reprocess records.
Question 738 of 1,616
Lambda Idempotent Processing with Kinesis — Duplicate Record Handling
This DVA-C02 practice question tests your understanding of deployment. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 developer is deploying an AWS Lambda function that processes data from an Amazon Kinesis stream. The function must be idempotent and handle duplicate records. The developer notices that the same record is being processed multiple times. What is the most likely cause of this issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
✓
The Kinesis stream's iterator age is too low, causing the function to reprocess records after a failure.
Option D is correct because when a Lambda function fails to process a record from a Kinesis stream, the iterator age (the time since the oldest record in the shard was read) can become too low, causing the function to reprocess records from the point of failure. This happens because Lambda uses the iterator age to determine where to resume reading after a failure, and if the age is low, it may restart from an earlier position, leading to duplicate processing. Idempotency is required precisely because Kinesis guarantees at-least-once delivery, and failures or throttling can cause the same record to be delivered multiple times.
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.
- ✗
The Kinesis data stream's retention period is too long, causing old records to be reprocessed.
Why it's wrong here
Retention period does not cause reprocessing.
- ✗
The function's reserved concurrency is set too low, causing invocations to be throttled and retried.
Why it's wrong here
Throttled invocations are not retried automatically for Kinesis.
- ✗
The batch size is set too high, causing the function to process records in multiple batches.
Why it's wrong here
Batch size affects batch processing, not duplicate processing.
- ✓
The Kinesis stream's iterator age is too low, causing the function to reprocess records after a failure.
Why this is correct
Low iterator age means the function may fall behind and reprocess records.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse the iterator age (which controls reprocessing after failures) with the retention period (which controls how long data is stored), leading them to incorrectly select Option A.
Detailed technical explanation
How to think about this question
Under the hood, Lambda polls the Kinesis stream using the Kinesis Client Library (KCL) and tracks the sequence number of the last successfully processed record. If the function fails, Lambda updates the iterator age and may reprocess records from the last checkpoint, which can be earlier than the failed record, causing duplicates. In real-world scenarios, this is common when the function has a long processing time or when the Kinesis stream has multiple shards, as each shard maintains its own iterator and checkpoint state.
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?
Deployment — This question tests Deployment — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Kinesis stream's iterator age is too low, causing the function to reprocess records after a failure. — Option D is correct because when a Lambda function fails to process a record from a Kinesis stream, the iterator age (the time since the oldest record in the shard was read) can become too low, causing the function to reprocess records from the point of failure. This happens because Lambda uses the iterator age to determine where to resume reading after a failure, and if the age is low, it may restart from an earlier position, leading to duplicate processing. Idempotency is required precisely because Kinesis guarantees at-least-once delivery, and failures or throttling can cause the same record to be delivered multiple times.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
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