Databricks Certified Data Engineer Professional Practice Mode

Community Discussion

Written by other learners. Comments can disagree with the marked answer — check the official documentation when in doubt.

• Chose E1

  Correct: E - Using VACUUM operation data is permamently removed that are older than 7 days by default. Sunday 1am - job completes, marking records as deleted in the transcation log (this is how the delete works in delta lake) Monday 3am (26 hours later): first VACUUM runs, but the deleted dat files are less than 7 days old (only 1 day and 2 hours), so they are not removed. Next Monday 3 am (8 days later counting from Sunday) - VACUUM runs again, and now the files are older than the 7-day threshold, so they are permanently deleted. Incorrect: A, B - Default data renention threshold is 7 days, not 24 hours. C - Time travel is limited by VACUUM operations. Deleted records are not accessible after this operation covers those records. D - The DELETE operations are logical in delta lake, not immediate physical deletetions.

• Chose E1

  Delta Lake’s time travel feature allows users to access previous versions of a table. Deleted data is not physically removed from storage immediately — instead, the files are logically marked for deletion, but retained for 7 days by default to support time travel and recovery. The VACUUM command is responsible for physically removing these obsolete files. However, to prevent accidental data loss, Delta Lake enforces a default retention threshold of 7 days (168 hours), meaning you cannot vacuum files younger than 7 days unless you override the retention check with a flag like retain 0 hours (which is strongly discouraged in production). So even if a delete is issued on Sunday at 1am and VACUUM is run on Monday at 3am, the deleted files won’t be physically removed unless the retention threshold is overridden — hence, they remain accessible via time travel for up to 7 days.

• Chose B2

  Since the VACUUM job runs every Monday at 3am, and deletes happen on Sundays at 1am, the deleted data files remain accessible via time travel for approximately 24 hours (until VACUUM removes them).