The answer is to add a random prefix to the S3 object key, which distributes writes across multiple prefixes. This resolves the issue because S3 enforces a PUT request rate limit of 3,500 objects per second per prefix, and with 10 MB/s of 2 KB records, the Lambda function is generating 5,000 PUT requests per second—exceeding that limit. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of S3 performance best practices and how Lambda interacts with S3 throttling, often appearing as a trap where increasing Lambda concurrency seems logical but actually worsens the problem. A common memory tip is to think of S3 prefixes like checkout lanes: more lanes (prefixes) mean more customers (requests) can be served simultaneously without a bottleneck.
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. 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 IoT sensor data. The data is processed by an AWS Lambda function that transforms the records and writes to an Amazon S3 bucket. Recently, the Lambda function has been failing with 'Rate exceeded' errors for the S3 PUT API calls. The data volume is 10 MB/s with average record size 2 KB. What should be done to resolve this issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a random prefix to the S3 object key to distribute writes across multiple prefixes
Option A is correct because S3 has a PUT request rate limit of 3,500 objects/s per prefix. With 10 MB/s and 2 KB records, that's 5,000 records/s, exceeding the limit. Increasing the number of S3 prefixes distributes writes across multiple partitions. Option B (increase Lambda concurrency) would worsen the issue. Option C (increase Kinesis shards) doesn't address S3 throttling. Option D (use Firehose) may help but is a bigger change; adding prefixes is simpler.
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.
✓
Add a random prefix to the S3 object key to distribute writes across multiple prefixes
Why this is correct
Random prefixes increase the number of S3 partitions, raising the PUT request limit.
Related concept
Read the scenario before looking for a memorised answer.
✗
Switch to Amazon Kinesis Data Firehose to write to S3
Why it's wrong here
Firehose can batch records and reduce PUT requests, but adding prefixes is a simpler fix.
✗
Increase the Lambda function's reserved concurrency
Why it's wrong here
More concurrent Lambda invocations would increase the PUT request rate, making throttling worse.
✗
Increase the number of Kinesis shards
Why it's wrong here
More shards increase parallelism but don't change the S3 rate limit issue.
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 DEA-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 Ingestion and Transformation — This question tests Data Ingestion and Transformation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add a random prefix to the S3 object key to distribute writes across multiple prefixes — Option A is correct because S3 has a PUT request rate limit of 3,500 objects/s per prefix. With 10 MB/s and 2 KB records, that's 5,000 records/s, exceeding the limit. Increasing the number of S3 prefixes distributes writes across multiple partitions. Option B (increase Lambda concurrency) would worsen the issue. Option C (increase Kinesis shards) doesn't address S3 throttling. Option D (use Firehose) may help but is a bigger change; adding prefixes is simpler.
What should I do if I get this DEA-C01 question wrong?
Identify which DEA-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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