Quote Originally Posted by Exmo View Post
"Just cache the result" while forgetting you need to check the cache on every request, which is the point of the cache. Checking the cache is a logical check. Making a cache isn't a magical thing that solves all problems. It's still N^N logical checks, but also you need to maintain the cache every time someone changes their blacklist or enters or leaves the instance (or did you want a memory leak that kills the entire server?).
That depends how they're handling the data and how you cache the results. Yes, they need to check to see if data for a player should be sent but that isn't an expensive operation. Yes, they need to update/clear the cache every once in a while. No, that isn't a big deal either.