The answer is the S3 destination bucket being located in a different AWS Region than the Kinesis application. This is the most likely cause because cross-region data transfer introduces significant network latency and increases the risk of checkpoint failures in Apache Flink, which relies on consistent, low-latency writes to its sink for state snapshots. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this scenario tests your understanding of how Flink’s checkpointing mechanism is sensitive to sink performance, and it’s a common trap to overlook Region alignment when troubleshooting high latency. A helpful memory tip is “Flink fails when sinks cross rails”—keeping your S3 sink in the same Region as your Flink application avoids the added network hop and ensures stable checkpoints.
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 using Amazon Kinesis Data Analytics for Apache Flink to process real-time sensor data. The application reads from a Kinesis data stream, performs windowed aggregations, and writes results to an S3 bucket. Recently, the application has been experiencing high latency and checkpoint failures. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The S3 destination bucket is located in a different AWS Region than the Kinesis application
Option C is correct. If the S3 bucket is in a different region, cross-region data transfer can introduce latency and checkpoint failures. Option A (parallelism) would cause resource issues, not necessarily checkpoint failures. Option B (shard count) would cause throttling. Option D (record size) is limited to 1 MB.
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.
✗
The number of shards in the Kinesis stream is insufficient for the data volume
Why it's wrong here
Insufficient shards cause throttling, not checkpoint failures.
✓
The S3 destination bucket is located in a different AWS Region than the Kinesis application
Why this is correct
Cross-region writes increase latency and can cause checkpoint timeouts.
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.
✗
The record size in the Kinesis stream exceeds the 1 MB limit
Why it's wrong here
Kinesis enforces a 1 MB limit; exceeding it would cause write errors.
✗
The parallelism of the Flink application is set too low for the number of shards
Why it's wrong here
Low parallelism may cause backpressure but not checkpoint failures directly.
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
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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 — 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: The S3 destination bucket is located in a different AWS Region than the Kinesis application — Option C is correct. If the S3 bucket is in a different region, cross-region data transfer can introduce latency and checkpoint failures. Option A (parallelism) would cause resource issues, not necessarily checkpoint failures. Option B (shard count) would cause throttling. Option D (record size) is limited to 1 MB.
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.
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