Sure, here are a couple of the examples, in priority order.
1. I have a few different use cases for putting dates (number format, seconds of ms is normal) on the vectors as a way to only bring back candidates after (>=) X and before (<) Y. Basically, Temporal limitations.
2. I have a list of arbitrary attributes, call it categorical information. Filter vectors where X is in that list. Or filter vectors where X is not in that list.