Subscriptions are made on nostrdb, and the same subs are made on remote relays. The only thing the network code does is call ndb_process_event, this feeds the notes to a multithreaded ingester that can de-dupe without even parsing the entire json blob so it’s crazy fast. When ingesting it verifies signatures, collects like stats, indexes and parses contents, stores in a compact binary format, parses profiles into flatbuffers, etc. Once it’s done processing it lets the local subscriptions know if they are looking for it.

So client code only ever talks to the local relay (nostrdb), and the UI code doesn’t have to do any processing. Everything is there once its ready.