The correct choice is to modify the Glue job to use a query parameter that selects only new or modified rows based on a timestamp column. This directly addresses the bottleneck by filtering data at the source, so instead of reading all 10 million rows and relying on job bookmarks to skip already-processed records, Glue pushes the WHERE clause down to the MySQL database, drastically reducing the data transferred during the JDBC read phase. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of pushdown predicates versus post-read filtering—a common trap is assuming more DPUs or larger fetch sizes will fix a read bottleneck, but the real constraint is often the database’s ability to serve data, not Glue’s parallelism. Remember the memory tip: “Filter at the source, not after the course”—always push your incremental logic into the query parameter to optimize Glue JDBC reads for incremental data.
DEA-C01 Data Operations and Support Practice Question
This DEA-C01 practice question tests your understanding of data operations and support. 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 uses AWS Glue to run ETL jobs that process data from an Amazon RDS for MySQL database and load it into an Amazon S3 data lake. The Glue job runs daily and processes incremental data. Recently, the job has been taking longer than expected. The engineer checks the CloudWatch logs and sees that the job is spending most of its time on the 'Reading from JDBC' phase. The MySQL table has 10 million rows and is indexed on the primary key. The Glue job uses a 'job bookmark' to track processed data. The engineer wants to improve the performance of the read phase. Which action is most likely to help?
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.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Modify the job to use a 'query' parameter that selects only the new or modified rows based on a timestamp column.
Option B is correct because using a 'query' parameter with a WHERE clause that filters on the bookmark key (e.g., a timestamp column) allows Glue to read only the incremental data, reducing the amount of data transferred. Option A is wrong because increasing the number of DPUs adds parallelism but the bottleneck may be the database's ability to serve data. Option C is wrong because increasing the fetch size may cause memory issues. Option D is wrong because job bookmark already tracks processed data; disabling it would cause reprocessing.
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 JDBC 'fetchSize' parameter to 10000.
Why it's wrong here
A larger fetch size reduces round trips but each fetch retrieves more data, which may not help if the issue is data volume.
✗
Disable job bookmark and perform a full refresh each time.
Why it's wrong here
Full refresh would read all 10 million rows every run, making the job slower.
✗
Increase the number of DPUs for the Glue job.
Why it's wrong here
More DPUs increase parallelism, but the database may not be able to handle multiple concurrent connections efficiently.
✓
Modify the job to use a 'query' parameter that selects only the new or modified rows based on a timestamp column.
Why this is correct
By filtering at the source, less data is read and transferred, speeding up the read phase.
Clue confirmation
The clue words "most likely", "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 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.
Identify which DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Data Operations and Support — This question tests Data Operations and Support — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Modify the job to use a 'query' parameter that selects only the new or modified rows based on a timestamp column. — Option B is correct because using a 'query' parameter with a WHERE clause that filters on the bookmark key (e.g., a timestamp column) allows Glue to read only the incremental data, reducing the amount of data transferred. Option A is wrong because increasing the number of DPUs adds parallelism but the bottleneck may be the database's ability to serve data. Option C is wrong because increasing the fetch size may cause memory issues. Option D is wrong because job bookmark already tracks processed data; disabling it would cause reprocessing.
What should I do if I get this DEA-C01 question wrong?
Identify which DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely", "primary". 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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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