Remote search results with restricted local index

Hello everyone,

I have an local index with websites most dear to me and that I regularily recrawl to keep the local index up to date. I’d like to integrate remote search results in the search but if I enable this, my index gets immediately polluted with lots of irrelevant URLs and the storage usage exceeds the system resources.

Is it possible to enable remote search but prevent the pollution of the local index?
Or as alternative: crawl to different collections (local → persistent, remote → clear regularily)?

Best regards
Chris