Google Cloud Professional Data Engineer · Free practice question 1 of 12
Sliding windows for moving averages
A card-fraud pipeline at Ivybridge Payments must compute, for every card, the average transaction amount over the previous 10 minutes, and refresh that figure every minute as events stream in through Dataflow. Which windowing strategy fits?
- A.Fixed windows of one minute
- B.Session windows with a 10-minute gap
- C.Fixed windows of 10 minutes
- D.Sliding windows 10 minutes long that start every minute
Show answer and explanation
Correct answer: D. Sliding windows 10 minutes long that start every minute
Why: Sliding (hopping) windows overlap: each one covers 10 minutes, and a new one begins every minute, so each card gets a fresh 10-minute average once a minute. One-minute fixed windows only see one minute of data, and 10-minute fixed windows update only once every 10 minutes. Session windows depend on gaps in activity, not a rolling time span.
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