The answer is to use a job parameter to store the last processed timestamp with millisecond precision and query records greater than that value. This is correct because AWS Glue job bookmarks natively track timestamps with only second precision, meaning any records inserted or modified within the same second but with microsecond differences will be missed when the job resumes. By storing a custom high-precision timestamp as a job parameter and using a WHERE clause to filter for records greater than that stored value, you bypass the bookmark’s limitation and capture every new or modified row. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of Glue’s bookmark granularity and the need for custom state management when source systems use sub-second precision. A common trap is assuming bookmarks handle all precision levels automatically, but they do not. Remember the memory tip: “Bookmarks stop at seconds; custom parameters capture the microseconds.”
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. 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 company has a Glue ETL job that reads from an Amazon RDS for MySQL table and writes to Amazon S3. The job runs hourly and processes new records based on a 'last_modified' timestamp column. Recently, the job started missing some records because the timestamp in MySQL is stored with microsecond precision but Glue's job bookmark only tracks second precision. Which solution addresses this issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a job parameter to store the last processed timestamp with millisecond precision and query records greater than that value.
Option A is correct because AWS Glue job bookmarks track timestamps with only second precision, so records with microsecond differences within the same second are missed. By using a custom job parameter to store the last processed timestamp with millisecond precision and querying records greater than that value, you bypass Glue's bookmark limitation and capture all new or modified records.
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.
✓
Use a job parameter to store the last processed timestamp with millisecond precision and query records greater than that value.
Why this is correct
Custom job bookmark with higher precision.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the job frequency to every 30 minutes.
Why it's wrong here
Does not solve the precision problem.
✗
Run a full refresh of the table each time instead of incremental.
Why it's wrong here
Inefficient and not recommended.
✗
Modify the MySQL table to use a DATE data type instead of TIMESTAMP.
Why it's wrong here
Loses time information entirely.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume Glue job bookmarks automatically handle all timestamp precisions, but the exam tests awareness that bookmarks default to second-level granularity and that custom logic is required for sub-second precision.
Detailed technical explanation
How to think about this question
MySQL's TIMESTAMP type can store fractional seconds up to microsecond precision (6 digits), while AWS Glue job bookmarks store the last processed timestamp as a Unix epoch in seconds (integer). This mismatch means that if two records have the same second but different microsecond values, only the first may be captured. A custom job parameter approach using a high-precision timestamp (e.g., '2025-03-15 12:00:00.123456') and a WHERE clause like 'last_modified > ?' ensures all records are processed, though you must manage state persistence (e.g., in DynamoDB or a parameter store) across job runs.
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.
TExam Day Tips
→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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Data Ingestion and Transformation — This question tests Data Ingestion and Transformation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a job parameter to store the last processed timestamp with millisecond precision and query records greater than that value. — Option A is correct because AWS Glue job bookmarks track timestamps with only second precision, so records with microsecond differences within the same second are missed. By using a custom job parameter to store the last processed timestamp with millisecond precision and querying records greater than that value, you bypass Glue's bookmark limitation and capture all new or modified records.
What should I do if I get this DEA-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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