- A
Configure the Lambda function with a reserved concurrency of 1 and a batch size of 1 to process records sequentially.
This ensures in-order processing per shard, and with proper idempotency, exactly-once can be achieved.
- B
Use the Kinesis Producer Library (KPL) with a sequence number for each record.
KPL supports exactly-once semantics per shard by using sequence numbers.
- C
Use Amazon SQS FIFO queues to decouple Kinesis and Lambda, ensuring ordering and exactly-once delivery.
Why wrong: SQS FIFO queues can receive messages from Lambda, but not directly from Kinesis without custom code.
- D
Enable S3 Event Notifications to trigger Lambda for each object.
Why wrong: S3 Event Notifications are at-least-once and do not guarantee ordering.
- E
Use Kinesis Data Firehose to buffer and deliver data to S3, then use Lambda to process.
Why wrong: Firehose does not provide exactly-once processing; it may deliver duplicates.
Quick Answer
The correct answer involves using the Kinesis Producer Library (KPL) with a sequence number for each record and configuring AWS Lambda with a reserved concurrency of 1 and a batch size of 1. This works because Kinesis Data Streams assigns a unique sequence number per shard, enabling exactly-once processing when the consumer tracks and commits these offsets, while Lambda’s single-threaded, single-record execution within a shard preserves strict ordering. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this scenario tests your understanding of streaming guarantees under the “Data Engineering” domain, often appearing as a trap where candidates confuse Kinesis Data Firehose or SQS FIFO—neither of which integrates with Kinesis for ordered, exactly-once delivery. A common pitfall is assuming S3 can enforce order, but S3 offers no ordering guarantees. Memory tip: think “KPL sequence + Lambda single” to recall the pair that locks in both exactly-once and ordering within a shard.
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. 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 data engineer is building a data pipeline that ingests streaming data from Amazon Kinesis Data Streams, transforms the data using AWS Lambda, and stores the results in Amazon S3. The engineer needs to ensure that each record is processed exactly once and in order. Which TWO approaches should the engineer consider? (Choose TWO.)
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
Configure the Lambda function with a reserved concurrency of 1 and a batch size of 1 to process records sequentially.
Option A is correct because Kinesis Data Streams supports exactly-once processing within a shard using the sequence number. Option E is correct because AWS Lambda can be configured with a reserved concurrency of 1 and a batch size of 1 to process records in order. Option B is incorrect because S3 does not provide ordering guarantees. Option C is incorrect because Kinesis Data Firehose does not guarantee exactly-once delivery. Option D is incorrect because SQS FIFO does not integrate directly with Kinesis.
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.
- ✓
Configure the Lambda function with a reserved concurrency of 1 and a batch size of 1 to process records sequentially.
Why this is correct
This ensures in-order processing per shard, and with proper idempotency, exactly-once can be achieved.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Use the Kinesis Producer Library (KPL) with a sequence number for each record.
Why this is correct
KPL supports exactly-once semantics per shard by using sequence numbers.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use Amazon SQS FIFO queues to decouple Kinesis and Lambda, ensuring ordering and exactly-once delivery.
Why it's wrong here
SQS FIFO queues can receive messages from Lambda, but not directly from Kinesis without custom code.
- ✗
Enable S3 Event Notifications to trigger Lambda for each object.
Why it's wrong here
S3 Event Notifications are at-least-once and do not guarantee ordering.
- ✗
Use Kinesis Data Firehose to buffer and deliver data to S3, then use Lambda to process.
Why it's wrong here
Firehose does not provide exactly-once processing; it may deliver duplicates.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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.
What to study next
Got this wrong? Here's your next step.
Identify which MLS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Questions learners often ask
What does this MLS-C01 question test?
Data Engineering — This question tests Data Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure the Lambda function with a reserved concurrency of 1 and a batch size of 1 to process records sequentially. — Option A is correct because Kinesis Data Streams supports exactly-once processing within a shard using the sequence number. Option E is correct because AWS Lambda can be configured with a reserved concurrency of 1 and a batch size of 1 to process records in order. Option B is incorrect because S3 does not provide ordering guarantees. Option C is incorrect because Kinesis Data Firehose does not guarantee exactly-once delivery. Option D is incorrect because SQS FIFO does not integrate directly with Kinesis.
What should I do if I get this MLS-C01 question wrong?
Identify which MLS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 20, 2026
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