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Question 1,342 of 1,755

Data Engineering →easyMultiple ChoiceObjective-mapped

Diagnose Lambda Throttling from Kinesis Due to Concurrency Limit

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 is streaming clickstream data from a website to Amazon Kinesis Data Streams. The data is consumed by a Lambda function that enriches each record with geolocation information before writing to an S3 bucket. Recently, the Lambda function has been failing with throttling errors. What is the MOST likely cause?

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.

A
The Lambda function's payload size exceeds the 6 MB limit
Why wrong: Kinesis records are limited to 1 MB, so payload size is not the issue.
B
The Lambda function's concurrent execution limit has been reached
Lambda throttles when the number of concurrent executions exceeds the account limit.
C
The Lambda function's reserved concurrency is set too high
Why wrong: High reserved concurrency would help, not cause throttling.
D
The Kinesis stream has exceeded the default shard limit of 500
Why wrong: Shard limit is a Kinesis limit, not Lambda. Throttling errors occur in Lambda.

Full breakdown with real-world context →

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 Lambda function's concurrent execution limit has been reached

The most likely cause is that the Lambda function's concurrent execution limit has been reached. Kinesis Data Streams invokes Lambda functions per shard, and with high throughput or many shards, concurrent invocations can exceed the default Lambda concurrency limit (1000 per region). This results in throttling errors. Option A is incorrect because the Lambda payload limit for asynchronous invocation (used by Kinesis) is 256 KB, not 6 MB. Option C is incorrect; setting reserved concurrency too high would not cause throttling—it could actually help avoid throttling. Option D is incorrect because the default shard limit is 500, but shard limits are a Kinesis concern, not directly causing Lambda throttling.

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 Lambda function's payload size exceeds the 6 MB limit
Why it's wrong here
Kinesis records are limited to 1 MB, so payload size is not the issue.
✓
The Lambda function's concurrent execution limit has been reached
Why this is correct
Lambda throttles when the number of concurrent executions exceeds the account limit.
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.
✗
The Lambda function's reserved concurrency is set too high
Why it's wrong here
High reserved concurrency would help, not cause throttling.
✗
The Kinesis stream has exceeded the default shard limit of 500
Why it's wrong here
Shard limit is a Kinesis limit, not Lambda. Throttling errors occur in Lambda.

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.

Quick reference

AWS S3 Storage Class Comparison

Storage Class	Min Duration	Retrieval	Use Case
S3 Standard	None	Immediate	Frequently accessed data
S3 Standard-IA	30 days	Immediate	Infrequent access, rapid retrieval
S3 One Zone-IA	30 days	Immediate	Non-critical infrequent data
S3 Intelligent-Tiering	None	Immediate–hours	Unknown or changing access patterns
S3 Glacier Instant	90 days	Milliseconds	Archive with instant retrieval
S3 Glacier Flexible	90 days	Minutes–hours	Archive, flexible retrieval
S3 Glacier Deep Archive	180 days	Hours	Long-term compliance archive

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: The Lambda function's concurrent execution limit has been reached — The most likely cause is that the Lambda function's concurrent execution limit has been reached. Kinesis Data Streams invokes Lambda functions per shard, and with high throughput or many shards, concurrent invocations can exceed the default Lambda concurrency limit (1000 per region). This results in throttling errors. Option A is incorrect because the Lambda payload limit for asynchronous invocation (used by Kinesis) is 256 KB, not 6 MB. Option C is incorrect; setting reserved concurrency too high would not cause throttling—it could actually help avoid throttling. Option D is incorrect because the default shard limit is 500, but shard limits are a Kinesis concern, not directly causing Lambda throttling.

What should I do if I get this MLS-C01 question wrong?

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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This MLS-C01 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 MLS-C01 exam.