- A
Increase the number of shards to 200 to provide more throughput.
Why wrong: The ingestion rate is low; more shards will not reduce iterator age if the consumer is the bottleneck.
- B
Increase the CPU capacity of the ECS task by moving to a larger instance type.
Why wrong: CPU utilization is low, so CPU is not the bottleneck.
- C
Move the destination from DynamoDB to Amazon RDS to reduce write latency.
Why wrong: The destination is not the bottleneck; the issue is processing capacity.
- D
Scale the number of KCL workers to match the number of shards (e.g., 50 workers) to process shards in parallel.
A single worker can only process one shard at a time; with 50 shards, records in other shards wait. Multiple workers can process shards concurrently, reducing latency.
Quick Answer
The correct answer is to scale the number of KCL workers to match the number of shards, such as deploying 50 workers. This is because the Kinesis Client Library (KCL) worker scaling principle dictates that a single worker can only process one shard at a time, leaving the other 49 shards idle and causing the iterator age to climb even when CPU is low. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this scenario tests your understanding of KCL’s record processor model and the common pitfall of confusing shard capacity with consumer parallelism—a frequent trap where candidates mistakenly blame DynamoDB or ingestion limits. The key insight is that KCL workers are the unit of consumption, not compute; each shard requires its own dedicated worker for true parallel processing. Memory tip: “One worker, one shard—more shards, more workers.”
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
You are a data engineer at a fintech company. The company processes real-time stock market data from multiple exchanges. The data is ingested via Amazon Kinesis Data Streams with 50 shards. Each record is about 1 KB, and the ingestion rate is 5,000 records per second. The data is consumed by a Java application running on Amazon ECS that performs real-time analytics and stores results in Amazon DynamoDB. Recently, the application has been experiencing high latency, and some records are stuck in the shards for minutes before being consumed. The CloudWatch metrics show that the application's CPU utilization is low, but the iterator age is increasing. The application uses the Kinesis Client Library (KCL) with a single worker. What is the most likely cause and how should it be fixed?
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.
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
Scale the number of KCL workers to match the number of shards (e.g., 50 workers) to process shards in parallel.
Option C is correct because a single KCL worker can only process one shard at a time; with 50 shards, records sit idle. Increasing the number of workers (e.g., to 50) allows parallel processing of all shards, reducing iterator age. Option A is wrong because the ingestion rate is well within the 50 shards' capacity (50 MB/s write vs ~5 MB/s actual). Option B is wrong because CPU is low, not high. Option D is wrong because DynamoDB is not part of the ingestion path.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 number of shards to 200 to provide more throughput.
Why it's wrong here
The ingestion rate is low; more shards will not reduce iterator age if the consumer is the bottleneck.
- ✗
Increase the CPU capacity of the ECS task by moving to a larger instance type.
Why it's wrong here
CPU utilization is low, so CPU is not the bottleneck.
- ✗
Move the destination from DynamoDB to Amazon RDS to reduce write latency.
Why it's wrong here
The destination is not the bottleneck; the issue is processing capacity.
- ✓
Scale the number of KCL workers to match the number of shards (e.g., 50 workers) to process shards in parallel.
Why this is correct
A single worker can only process one shard at a time; with 50 shards, records in other shards wait. Multiple workers can process shards concurrently, reducing latency.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related MLS-C01 NAT questions on configuration and troubleshooting.
- →
Data Engineering — study guide chapter
Learn the concepts, then practise the questions
- →
Data Engineering practice questions
Targeted practice on this topic area only
- →
All MLS-C01 questions
1,755 questions across all exam domains
- →
AWS Certified Machine Learning Specialty MLS-C01 study guide
Full concept coverage aligned to exam objectives
- →
MLS-C01 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related MLS-C01 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Data Engineering practice questions
Practise MLS-C01 questions linked to Data Engineering.
Machine Learning Implementation and Operations practice questions
Practise MLS-C01 questions linked to Machine Learning Implementation and Operations.
Modeling practice questions
Practise MLS-C01 questions linked to Modeling.
Exploratory Data Analysis practice questions
Practise MLS-C01 questions linked to Exploratory Data Analysis.
MLS-C01 fundamentals practice questions
Practise MLS-C01 questions linked to MLS-C01 fundamentals.
MLS-C01 scenario practice questions
Practise MLS-C01 questions linked to MLS-C01 scenario.
MLS-C01 troubleshooting practice questions
Practise MLS-C01 questions linked to MLS-C01 troubleshooting.
Practice this exam
Start a free MLS-C01 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this MLS-C01 question test?
Data Engineering — This question tests Data Engineering — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Scale the number of KCL workers to match the number of shards (e.g., 50 workers) to process shards in parallel. — Option C is correct because a single KCL worker can only process one shard at a time; with 50 shards, records sit idle. Increasing the number of workers (e.g., to 50) allows parallel processing of all shards, reducing iterator age. Option A is wrong because the ingestion rate is well within the 50 shards' capacity (50 MB/s write vs ~5 MB/s actual). Option B is wrong because CPU is low, not high. Option D is wrong because DynamoDB is not part of the ingestion path.
What should I do if I get this MLS-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related MLS-C01 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 20, 2026
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.