😕 Why would such a limit be specific to npubs? I can't imagine it would be more technically demanding to have a million npubs then a novel of the same data size.
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I mean demanding on the relay, btw. Most clients would probably just crash.
Npubs take space. 5000 users with average 2000 follows would use well over 650 MB of bandwidth in just a few minutes. Some clients are inefficient and same the same queries over and over. A relay handles terabytes of data per day.
Without limits some script kiddie will start abusing things.
Right. Hadn't thought of the bandwidth component, only the storage one.
Maybe relays charge a few millisats per linked npub, from a budget paid for in advance. End users are charged similarly for each post they read.