That's only way how it can scale. Similar to DNS. You need to typed of relays. First your primary relay (or a few of them) for content you create. Then filtering relay which cashes and can search notes from people you follow aggregated from their respective primary relays.
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Fix Typos: That's only way how it can scale. Similar to DNS. You need two types of relays. First your primary relay (or a few of them) for content you create. Then filtering relay which caches and can search notes from people you follow aggregated from their respective primary relays. Filtering or caching relays can be ephemeral each user needs to keep their original content on their primary relay.