Which window type is fixed-size, overlapping, and used only for JOIN operations?

Which window type is fixed-size, overlapping, and used only for JOIN operations?

• A. Tumbling Window
• B. Hopping Window
• C. Sliding Window
• D. Session Window

Answer: (B)

A hopping window is defined by a fixed window length and a separate hop (advance) interval. When the hop is smaller than the window length, consecutive windows overlap in time. That overlapping is exactly what makes hopping windows well-suited for time-based joins: an event from one stream can fall into multiple overlapping windows, increasing the chances of matching it with related events from another stream within a shared time frame. Tumbling windows are non-overlapping, so they don’t satisfy the overlap requirement. Sliding windows do overlap, but their primary use is continuous time-based aggregations rather than the specific overlapping-window pattern relied on for joining streams. Session windows are dynamic, based on gaps between events, and not fixed-size.

A hopping window is defined by a fixed window length and a separate hop (advance) interval. When the hop is smaller than the window length, consecutive windows overlap in time. That overlapping is exactly what makes hopping windows well-suited for time-based joins: an event from one stream can fall into multiple overlapping windows, increasing the chances of matching it with related events from another stream within a shared time frame.

Tumbling windows are non-overlapping, so they don’t satisfy the overlap requirement. Sliding windows do overlap, but their primary use is continuous time-based aggregations rather than the specific overlapping-window pattern relied on for joining streams. Session windows are dynamic, based on gaps between events, and not fixed-size.