Sorry for may be silly question but it is unclear from docs what is the unit of measurement for sliding window? Is it milliseconds, seconds or number of items in the stream? I've noticed the aggregation operation was producing empty results and I had to filter them explicitly because probably there was no data available for that window, so I guess last point it not an option.
Jet doesn't specify a unit for windows, instead the windows are calculated based on the same unit that your timestamps are specified in. Typically if your timestamps are UNIX-style timestamps then it would be in milliseconds, but you could also use nanoseconds, seconds, or minutes if that's how your timestamps are defined. It refers to specifically event time and is not related to number of events in the stream, only to their timestamps.