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Question 244 of 1,755

Data Engineering →hardMultiple ChoiceObjective-mapped

Reduce Kinesis Data Streams Iterator Age by Scaling Consumers

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 financial services company uses Amazon Kinesis Data Streams with 50 shards to ingest real-time stock trade data. The data is consumed by a custom Java application running on Amazon EC2 instances. Recently, the application has been experiencing high latency, and CloudWatch metrics show that the average iterator age is increasing. The application uses the Kinesis Client Library (KCL) with DynamoDB for lease tracking. The EC2 instances are in an Auto Scaling group with a minimum of 2 and maximum of 10 instances, and the current CPU utilization is below 50%. The team wants to reduce latency without increasing costs significantly. What should they do?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

A
Increase the provisioned read capacity of the DynamoDB lease table
Why wrong: Increasing the provisioned read capacity of the DynamoDB lease table is unnecessary because the lease table is not the bottleneck; lease operations consume minimal capacity and iterator age is driven by consumer processing speed.
B
Enable enhanced fan-out on the Kinesis stream
Why wrong: Enhanced fan-out is designed for multiple consumer applications to have dedicated 2 MB/second per shard throughput, but this scenario involves a single consumer group; it would not reduce latency for the existing consumer and would increase costs.
C
Increase the number of shards in the Kinesis stream
Why wrong: Increasing the number of shards would increase the stream's throughput capacity but also cost, and the current issue is that consumers cannot keep up with the existing shards; adding more shards would worsen the problem without improving consumer performance.
D
Increase the maximum size of the Auto Scaling group and set a scaling policy based on iterator age
Increasing the maximum size of the Auto Scaling group and setting a scaling policy based on iterator age allows more EC2 instances to be added dynamically, increasing the number of consumers processing shards in parallel, which directly reduces iterator age without significant cost increase.

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

✓

Increase the maximum size of the Auto Scaling group and set a scaling policy based on iterator age

Increasing the number of consumers (EC2 instances) by raising the Auto Scaling group maximum and setting a scaling policy based on iterator age allows more shards to be processed concurrently, reducing the iterator age. Option A is incorrect because the DynamoDB lease table is not the bottleneck; lease operations are lightweight and the current read capacity is sufficient. Option B is incorrect because enhanced fan-out is designed for multiple consumer applications to get dedicated throughput, but here there is a single consumer group; it would not reduce latency for the existing consumer and would add cost. Option C is incorrect because increasing shards would increase the stream's throughput capacity but also cost, whereas the current issue is consumer-side capacity, not stream capacity.

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.

✗
Increase the provisioned read capacity of the DynamoDB lease table
Why it's wrong here
Increasing the provisioned read capacity of the DynamoDB lease table is unnecessary because the lease table is not the bottleneck; lease operations consume minimal capacity and iterator age is driven by consumer processing speed.
✗
Enable enhanced fan-out on the Kinesis stream
Why it's wrong here
Enhanced fan-out is designed for multiple consumer applications to have dedicated 2 MB/second per shard throughput, but this scenario involves a single consumer group; it would not reduce latency for the existing consumer and would increase costs.
✗
Increase the number of shards in the Kinesis stream
Why it's wrong here
Increasing the number of shards would increase the stream's throughput capacity but also cost, and the current issue is that consumers cannot keep up with the existing shards; adding more shards would worsen the problem without improving consumer performance.
✓
Increase the maximum size of the Auto Scaling group and set a scaling policy based on iterator age
Why this is correct
Increasing the maximum size of the Auto Scaling group and setting a scaling policy based on iterator age allows more EC2 instances to be added dynamically, increasing the number of consumers processing shards in parallel, which directly reduces iterator age without significant cost increase.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
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.

Trap categories for this question

Scenario analysis trap
Enhanced fan-out is designed for multiple consumer applications to have dedicated 2 MB/second per shard throughput, but this scenario involves a single consumer group; it would not reduce latency for the existing consumer and would increase costs.

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: Increase the maximum size of the Auto Scaling group and set a scaling policy based on iterator age — Increasing the number of consumers (EC2 instances) by raising the Auto Scaling group maximum and setting a scaling policy based on iterator age allows more shards to be processed concurrently, reducing the iterator age. Option A is incorrect because the DynamoDB lease table is not the bottleneck; lease operations are lightweight and the current read capacity is sufficient. Option B is incorrect because enhanced fan-out is designed for multiple consumer applications to get dedicated throughput, but here there is a single consumer group; it would not reduce latency for the existing consumer and would add cost. Option C is incorrect because increasing shards would increase the stream's throughput capacity but also cost, whereas the current issue is consumer-side capacity, not stream capacity.

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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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