Same logic as a search engine might apply to the Web - some kind of crawling rules. That said, the network tends to use Relay services to optimize it. The Relay

Same logic as a search engine might apply to the Web - some kind of crawling rules. That said, the network tends to use Relay services to optimize it. The Relays are essentially dumb caches that provide a firehose from multiple servers. We introduced them to make it easier for new applications to pull from the network, but they're optional; you can setup your own relay or crawl/subscribe directly with servers. EDIT: to answer your question - this means the relay tends to decide what gets indexed.