Knowing very little about the internals of Hubble, I'm at risk of saying something totally useless, but have you checked Prolly Trees? I attended this presentation a couple of months ago, and I feel that it could be related to optimized hub sync. https://youtu.be/X8nAdx1G-Cs?si=1g5RdIKXg1S0mVA2&t=340

This is a very cool talk. Interestingly, it's almost exactly the same algorithm the hubs use right now. Prolly trees are more efficient since it collapses the number of levels required (we use timestamp prefix tries, so it always at least 10 levels), but apart from that it's exactly the same.

https://joelgustafson.com/posts/2023-05-04/merklizing-the-key-value-store-for-fun-and-profit blog post from the author