good point. It's a hard balance to strike. We currently expire events from npubs outside of our WoT faster than those within it. That way we can let clients handle filtering for recent events, and obviate the load from holding/processing older events. We're small though and every relay can do things differently.

if it ever ramps up to the point that its causing a denial of service, we can straight up block npubs outside our WoT at the relay.  Hopefully it never comes to that