The answer is to use enhanced fan-out, which gives each consumer its own dedicated 2 MB/second read throughput per shard. This directly addresses the DynamoDB write capacity bottleneck because, with the standard KCL consumer, all workers share a single 2 MB/second shard throughput and must poll the shard frequently, generating excessive writes to the DynamoDB lease table. Enhanced fan-out eliminates that polling overhead by pushing records to each consumer, drastically reducing lease table write operations and freeing up DynamoDB capacity for the actual fraud detection results. On the MLS-C01 exam, this scenario tests your understanding of Kinesis throughput mechanics and the trade-off between shared and dedicated consumers—a common trap is to confuse scaling EC2 instances or Lambda with solving a read-side bottleneck, when the real issue is contention for shard throughput. Remember the mnemonic: “Fan-out frees the lease; polling punishes the provisioned.”
MLS-C01 Data Engineering Practice Question
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 runs a real-time fraud detection system using Amazon Kinesis Data Streams with 100 shards. Data is consumed by a custom Java application running on Amazon EC2 instances in an Auto Scaling group. The application processes records and writes results to a DynamoDB table. Over the past month, the application has experienced intermittent slowdowns and the DynamoDB write capacity has been fully utilized during peak hours. The team wants to improve throughput without losing the ability to reprocess failed records. The application currently uses the Kinesis Client Library (KCL) with DynamoDB as the lease table. The team is considering the following changes: A. Increase the number of EC2 instances to match the number of shards. B. Switch to using AWS Lambda as the consumer to handle scaling automatically. C. Increase the write capacity of the DynamoDB lease table to handle more workers. D. Use enhanced fan-out to have each consumer receive its own 2 MB/second shard throughput. Which change should the team implement first to address the issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use enhanced fan-out to have each consumer receive its own 2 MB/second shard throughput.
The primary bottleneck is DynamoDB write capacity being fully utilized during peak hours. Enhanced fan-out (option B) provides each consumer with a dedicated 2 MB/second read throughput per shard, eliminating the need for consumers to contend for the shared 2 MB/second per shard. This reduces the load on the DynamoDB lease table because workers no longer need to poll for records, which in turn lowers the write operations to the lease table and alleviates the DynamoDB write capacity issue.
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 write capacity of the DynamoDB lease table to handle more workers.
Why it's wrong here
Lease table capacity is not the bottleneck.
✓
Use enhanced fan-out to have each consumer receive its own 2 MB/second shard throughput.
Why this is correct
Enhanced fan-out gives dedicated throughput per consumer.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Switch to using AWS Lambda as the consumer to handle scaling automatically.
Why it's wrong here
Lambda does not provide reprocessing capabilities.
✗
Increase the number of EC2 instances to match the number of shards.
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume increasing DynamoDB write capacity (option A) is the direct fix for write capacity exhaustion, but they miss that enhanced fan-out reduces the underlying cause of those writes by eliminating polling-based contention.
Detailed technical explanation
How to think about this question
Enhanced fan-out uses an HTTP/2 push model via the SubscribeToShard API, delivering records to each consumer at up to 2 MB/second per shard without polling. This eliminates the need for KCL workers to poll the shard, which reduces the frequency of DynamoDB lease table updates (used for checkpointing and lease coordination). In a real-world scenario, a single shard with 10 consumers would normally be limited to 2 MB/second total; enhanced fan-out gives each consumer its own 2 MB/second, dramatically improving throughput and reducing DynamoDB write pressure.
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.
TExam Day Tips
→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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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 enhanced fan-out to have each consumer receive its own 2 MB/second shard throughput. — The primary bottleneck is DynamoDB write capacity being fully utilized during peak hours. Enhanced fan-out (option B) provides each consumer with a dedicated 2 MB/second read throughput per shard, eliminating the need for consumers to contend for the shared 2 MB/second per shard. This reduces the load on the DynamoDB lease table because workers no longer need to poll for records, which in turn lowers the write operations to the lease table and alleviates the DynamoDB write capacity issue.
What should I do if I get this MLS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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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