Google Cloud Professional Data Engineer Exam

Which windowing strategy would be ineffective for processing data with frequent gaps in activity?

1. Tumbling windows

2. Global window

3. Hopping windows

4. Session windows

The correct answer is: Session windows

The choice of session windows is particularly relevant when dealing with data that has frequent gaps in activity. Session windows are designed to group events that are related by time; they dynamically create windows based on the activity and inactivity periods of the data stream. This means that if there are intervals of time without any events, session windows can effectively create smaller windows that only cover periods where events occur, thus accommodating irregular activity. However, if the data input has frequent gaps, session windows may end up being inefficient because they require a certain level of activity to define the boundaries of the windows. If there are long periods of inactivity, this can lead to many small, empty windows or can even risk missing out on relevant periods of data that follow those gaps. This makes session windows less effective for capturing and processing data patterns where regularity and consistency are necessary for optimal performance. In contrast, other strategies like tumbling and hopping windows apply fixed intervals regardless of activity, while global windows simply encompass the entire data set. These other windowing strategies can function accurately even without consistent activity, emphasizing their validity compared to session windows in such scenarios.