Published npm package nostr-social-graph and its demo on https://search.iris.to
It builds a social graph from Nostr follow events. You can query followed users, followers and follow distances. You can change the graph root user, efficiently calculating new follow distances.
It maps public keys to integers as internal representation, consuming less memory and storage when serialized. My graph of 23 000 users and 120 000 follow relationships is 2.2 MB on disk.
The package also includes pre-crawled datasets of follows and profiles that you can optionally use. They're used on https://beta.iris.to and https://search.iris.to for hydrating the search index and profile cache.
https://beta.iris.to uses the social graph for filtering of replies and notification, so you don't need to see that reply guy again (unless he's followed by people you follow — need to add "muted by followed users" support).
