Subdomain 1.3: Ensure temporal integrity and feature consistency.
1.An ML engineer is generating a training dataset by joining a labels table with a feature view that contains daily-updated transaction aggregates. The feature view SQL uses a standard `GROUP BY` query without an explicit timestamp. What is the likely consequence of using this feature view for point-in-time training set generation?
- A.The training set will correctly reflect historical values because the feature view is evaluated at event times.
- B.The training set will contain leakage because the aggregate uses future data relative to some label events.
- C.The training set generation will automatically detect and extract a timestamp from the feature view's base table.
- D.The training set will only include labels that align with the feature view's refresh schedule.
Show answer & explanation
Correct answer: B — The training set will contain leakage because the aggregate uses future data relative to some label events.
- A. Incorrect. Without an explicit timestamp in the feature view, the aggregates are not tied to a specific point in time, so the training set cannot correctly reflect historical values at event times. The standard GROUP BY aggregate can include data from after the label timestamp, breaking point-in-time correctness.
- B. Correct. Because the feature view lacks an explicit timestamp, the aggregate is computed over all available data, including records that occurred after some label events. This introduces temporal leakage in the training set, making the point-in-time join invalid.
- C. Incorrect. Snowflake does not automatically detect or infer an event timestamp from the base table for a generic GROUP BY feature view. Point-in-time correctness requires the feature definition to be explicitly time-aware.
- D. Incorrect. The refresh schedule of the feature view does not filter labels to only those that align with refresh times. The primary risk here is leakage, not label filtering.