This MLS-C01 practice question tests your understanding of data engineering. 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 company uses Amazon Kinesis Data Streams to ingest clickstream data. The stream has 8 shards. A Lambda function processes each record and writes to Amazon DynamoDB. The Lambda function sometimes fails due to DynamoDB write throttling, causing duplicate processing of records after retries. The data engineering team needs to ensure exactly-once processing semantics for the DynamoDB writes. What should the team do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use DynamoDB conditional writes with the Kinesis sequence number as a unique attribute to make writes idempotent.
Option B is correct because DynamoDB transactions allow conditional writes. Using the Kinesis sequence number as a condition check ensures idempotency: if a record with that sequence number already exists, the write is skipped. Option A is wrong because increasing write capacity may reduce throttling but does not guarantee exactly-once; duplicates can still occur. Option C is wrong because SQS delays are for visibility timeout, not idempotency. Option D is wrong because FIFO queues support exactly-once delivery but the Lambda would still need to deduplicate within the batch.
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 Amazon SQS FIFO queue between Kinesis and Lambda to deduplicate records.
Why it's wrong here
SQS FIFO provides exactly-once delivery but does not eliminate duplicates from retries within Lambda.
✗
Configure the Lambda event source mapping with a maximum retry count of 0 and a DLQ.
Why it's wrong here
This would drop records instead of ensuring exactly-once processing.
✗
Increase the DynamoDB write capacity units to avoid throttling.
Why it's wrong here
This reduces throttling but does not prevent duplicate processing of retried records.
✓
Use DynamoDB conditional writes with the Kinesis sequence number as a unique attribute to make writes idempotent.
Why this is correct
Conditional writes based on the sequence number ensure each record is written only once.
Related concept
Read the scenario before looking for a memorised answer.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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.
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: Use DynamoDB conditional writes with the Kinesis sequence number as a unique attribute to make writes idempotent. — Option B is correct because DynamoDB transactions allow conditional writes. Using the Kinesis sequence number as a condition check ensures idempotency: if a record with that sequence number already exists, the write is skipped. Option A is wrong because increasing write capacity may reduce throttling but does not guarantee exactly-once; duplicates can still occur. Option C is wrong because SQS delays are for visibility timeout, not idempotency. Option D is wrong because FIFO queues support exactly-once delivery but the Lambda would still need to deduplicate within the batch.
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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Question Discussion
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