The answer is that the new partition folder does not follow the Hive-style partition naming convention expected by the crawler. AWS Glue crawlers rely on a specific folder structure, such as `date=2023-01-01/`, to automatically detect and register new partitions in the Data Catalog. If the folder is named with a non-standard pattern like `2023-01-01/` or uses a different key-value format, the crawler will skip it entirely, even if configured to crawl all folders. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this question tests your understanding of how Glue integrates with S3 partition schemas and the importance of naming conventions in automated data discovery. A common trap is assuming the crawler will detect any new folder, but it strictly requires the Hive-style `key=value` pattern. Remember the mnemonic: “Hive-style, no file—the crawler won’t smile.”
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 data pipeline uses AWS Glue to crawl an S3 bucket and create a table in the AWS Glue Data Catalog. The data is in Parquet format with partitions by date. After a new partition is added to S3, the crawler runs but the new partition is not reflected in the table. 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 new partition folder does not follow the Hive-style partition naming convention expected by the crawler.
Option A is correct because the Glue crawler may be configured to only crawl new folders if the crawler's configuration is set to 'Crawl new folders only' but the partition path may not match the expected pattern, or the crawler's 'Schema updates' setting might be set to 'Ignore'. More commonly, the crawler's 'Update the table definition' option is set to 'Add new columns only' or 'Ignore the change and don't update the table'; the correct setting to add partitions is 'Add new columns only' or 'Add new partitions only'. However, the most typical issue is that the crawler is set to 'Crawl all folders each time' and still not picking up because the partition path is not in a recognized Hive-style format (e.g., date=2023-01-01/). Option A points to the partition path format. Option B is wrong because Glue can handle Parquet. Option C is wrong because the crawler does not need Lambda triggers. Option D is wrong because the crawler can handle up to many partitions.
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 crawler requires an AWS Lambda trigger to be configured for new partitions.
Why it's wrong here
Glue crawlers do not need Lambda triggers; they can run on schedule.
✗
The Parquet schema in the new partition does not match the existing table schema.
Why it's wrong here
Glue crawlers can merge schemas if configured, but the partition would still be added.
✓
The new partition folder does not follow the Hive-style partition naming convention expected by the crawler.
Why this is correct
Glue crawlers require partition folders to follow the key=value pattern to automatically detect partitions.
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 S3 bucket has too many partitions, exceeding the Glue crawler limit.
Why it's wrong here
Glue crawlers support up to 10 million partitions.
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 new partition folder does not follow the Hive-style partition naming convention expected by the crawler. — Option A is correct because the Glue crawler may be configured to only crawl new folders if the crawler's configuration is set to 'Crawl new folders only' but the partition path may not match the expected pattern, or the crawler's 'Schema updates' setting might be set to 'Ignore'. More commonly, the crawler's 'Update the table definition' option is set to 'Add new columns only' or 'Ignore the change and don't update the table'; the correct setting to add partitions is 'Add new columns only' or 'Add new partitions only'. However, the most typical issue is that the crawler is set to 'Crawl all folders each time' and still not picking up because the partition path is not in a recognized Hive-style format (e.g., date=2023-01-01/). Option A points to the partition path format. Option B is wrong because Glue can handle Parquet. Option C is wrong because the crawler does not need Lambda triggers. Option D is wrong because the crawler can handle up to many partitions.
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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