Yes. I describe this in this part of the article: https://overreacted.io/a-social-filesystem/#:~:text=One%20ch...
It's basically event sourcing. You listen to the data you care about from the network and update the local index (DB). There are also tools like Tap (https://docs.bsky.app/blog/introducing-tap) that do the plumbing work and let you backfill automatically.