Assuming you're not using the proposed streaming option, I suppose you could always send a webhook for that fact alone? In other words, an empty notification, with semantics of "something has probably changed, better poll the SCROLL if you aren't already".
replyDoesn't doing that just reinvent eTags on hypertext resources from the RESTful wars and XML Web Services days 20 years ago?
reply1. Long Poll the cursor to pull down the latest events
2. Trigger a long-poll even if in exponential backoff because they shot you a webhook saying 'eTag changed!'
If your API is just wrapping Kafka, it can long-poll
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