The answer is to use S3 event notifications to trigger AWS Glue jobs only for new files. This approach eliminates the need for full scans by invoking the Glue ETL job as soon as a new JSON metadata file lands in the S3 bucket, processing only that single 2 KB object instead of re-reading the entire bucket every hour. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this question tests your understanding of event-driven architecture for cost and latency optimization—a common scenario where candidates mistakenly choose increasing DPUs or converting to Parquet, but those still incur full-scan overhead. The key trap is assuming more compute or better compression alone solves the problem, when the real bottleneck is the scanning pattern itself. Memory tip: think “event, not sweep”—trigger on arrival, don’t re-scan the entire fleet.
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 media company ingests video metadata from multiple sources into an Amazon S3 bucket. Each metadata record is a JSON file about 2 KB. They use AWS Glue ETL jobs to process these files and load them into Amazon Redshift for analytics. The jobs currently run hourly and take about 10 minutes to process all new files. However, the company is growing and expects the number of files to increase 100x. The data engineering team wants to minimize processing time and cost. The Glue job currently reads all files from the S3 bucket using a full scan. What should they do to optimize the pipeline?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use S3 event notifications to trigger Glue jobs only for new files
Using S3 event notifications to trigger Glue jobs on new objects eliminates scanning and reduces latency. Option A is wrong because increasing DPUs costs more. Option B is wrong because consolidating files reduces number of objects. Option D is wrong because converting to Parquet helps but still scanning all files.
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.
✗
Consolidate the small JSON files into larger files using a scheduled job
Why it's wrong here
Consolidation helps but still requires scanning.
✗
Convert the data to Parquet format and partition it
Why it's wrong here
Improves performance but still scanning all partitions.
✗
Increase the number of Glue DPUs to process files faster
Why it's wrong here
Increases cost; scanning remains inefficient.
✓
Use S3 event notifications to trigger Glue jobs only for new files
Why this is correct
Event-driven eliminates full scan and reduces cost.
Clue confirmation
The clue word "minimum / minimize" 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
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.
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: Use S3 event notifications to trigger Glue jobs only for new files — Using S3 event notifications to trigger Glue jobs on new objects eliminates scanning and reduces latency. Option A is wrong because increasing DPUs costs more. Option B is wrong because consolidating files reduces number of objects. Option D is wrong because converting to Parquet helps but still scanning all files.
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: "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?
Static NAT maps one inside address to one outside address.
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Question Discussion
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