As far as I know, this is all cached at an instance level. So only the first person to pull something from your instance actually hits your instance's resources

As far as I know, this is all cached at an instance level. So only the first person to pull something from your instance actually hits your instance's resources. I can still see posts and users from dead instances because it's all cached on my instance. There's a rake task to wipe it, but people are advised not to since those caches have been what saved at least one instance whose name I can't remember.