- A
Use a FIFO queue as an event source instead of DynamoDB Streams.
Why wrong: DynamoDB Streams already provides ordering.
- B
Increase the Lambda function's concurrency limit.
Why wrong: May cause out-of-order processing.
- C
Set a reserved concurrency for the Lambda function to limit concurrent executions.
Prevents too many parallel invocations.
- D
Set the batch size to 1 in the event source mapping.
Ensures processing one item at a time in order.
- E
Enable the batch window in the event source mapping.
Why wrong: Not relevant for ordering.
Question 1,133 of 1,616
DynamoDB Stream Lambda Exactly Once and In-Order
This DVA-C02 practice question tests your understanding of development with aws services. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 using AWS Lambda with an Amazon DynamoDB trigger. The Lambda function processes items from a DynamoDB Stream. The developer needs to ensure that the function processes each change exactly once and in order. Which TWO configurations should the developer use?
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
✓
Set a reserved concurrency for the Lambda function to limit concurrent executions.
Option C is correct because setting a reserved concurrency for the Lambda function limits the number of concurrent executions, which prevents multiple shards from being processed simultaneously. This ensures that DynamoDB Stream records are processed in order within each shard, as the stream preserves order per shard but not across shards. Option D is correct because setting the batch size to 1 forces the Lambda function to process only one record per invocation, guaranteeing that each change is processed exactly once and in sequence without batching multiple records that could introduce ordering issues.
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 a FIFO queue as an event source instead of DynamoDB Streams.
Why it's wrong here
DynamoDB Streams already provides ordering.
- ✗
Increase the Lambda function's concurrency limit.
Why it's wrong here
May cause out-of-order processing.
- ✓
Set a reserved concurrency for the Lambda function to limit concurrent executions.
Why this is correct
Prevents too many parallel invocations.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Set the batch size to 1 in the event source mapping.
Why this is correct
Ensures processing one item at a time in order.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Enable the batch window in the event source mapping.
Why it's wrong here
Not relevant for ordering.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume increasing concurrency or using a FIFO queue will solve ordering issues, but they overlook that DynamoDB Streams already provide per-shard ordering and that limiting concurrency and batch size is the correct approach to enforce exactly-once and in-order processing.
Detailed technical explanation
How to think about this question
DynamoDB Streams guarantee ordering within a single shard, but when multiple shards are processed concurrently, the overall order across shards is not preserved. By setting reserved concurrency to 1, you effectively force the Lambda function to process one shard at a time, maintaining per-shard order. Additionally, setting batch size to 1 ensures that each invocation handles exactly one stream record, eliminating the risk of reordering or duplicate processing that can occur when batching multiple records in a single invocation.
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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Development with AWS Services — study guide chapter
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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: Set a reserved concurrency for the Lambda function to limit concurrent executions. — Option C is correct because setting a reserved concurrency for the Lambda function limits the number of concurrent executions, which prevents multiple shards from being processed simultaneously. This ensures that DynamoDB Stream records are processed in order within each shard, as the stream preserves order per shard but not across shards. Option D is correct because setting the batch size to 1 forces the Lambda function to process only one record per invocation, guaranteeing that each change is processed exactly once and in sequence without batching multiple records that could introduce ordering issues.
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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