Making your own atproto backlink index

For shelf.cafe I wanted to aggregate interesting conversations about a blog post in one place, so people can chat and learn. As part of this, I wanted to “discover” every time a blog post had been shared somewhere else, like Bluesky, and surface that. This is commonly referred to as a “backlink”. While building this out I tackled some very interesting technical challenges so here’s a little write up that covers looking up existing atproto backlinks, subscribing to the jetstream to monitor for new ones, and how to efficiently determine whether we care about a specific URL being mentioned somewhere on atproto. the jetstream The Bluesky team, in collaboration with the community, have and are developing some really interesting infrastructure that enables building on top of it with minimal effort. One of the most important pieces is the jetstream, which recently had a rework and a v2 version. I’ll just be talking about v2, but a lot of the existing ecosystem still use the original…