Thank you for the extended testing!
I can’t really wrap my head around why it would be slower running AJAX than not. If we wouldn’t run AJAX all the posts would be loaded in on page load which basically should make the server hit the memory limit and crash (I would think). Of course I’ll have to take your word for it since I’m afraid the best site I have to test it on still only have about 15k posts (It works decently there).
Perhaps there’s some AJAX tweaking that could be done to the relationship field and post object field to accommodate for huge quantities of posts.
I’ll ask @elliot to chime in 🙂
