Is this possible? Displaying threads on index with x criteria

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Yep. You can try to do that.

And maybe you need to update the cache for each (or several) action related to the thread, like edit, delete (post, thread, attachments), inline moderation (approve/unapprove/move post and thread), delete user, pruning users post, and etc. And/or maybe you can use or combine it with the task system.
Depends on how accurate you want the data to be displayed.

But I don't know about the cache size (depends on whatever data needed to be processed and whatever data needed to be displayed). If it is big enough, maybe you need to export it into a file.

Personally (only my personal opinion), in this case, I prefer to this in this way. I can't predict what my users do with their threads/posts/attachments.