To be fair, I’m not quite as concerned about the network performance, since unreal already only updates the changes from an array. It’s mostly the CPU performance when updating the map values on the client.
I did think about only replicating the “delta” as you put it, but for late joiners it’s going to require 2 arrays to be replicated. Assuming by delta you mean only the values that changed since the last time the array was replicated. If you mean just storing every variable that has changed over the lifetime of the server, then I feel like at some point we’re just back at square one.
Unless there is an overridable function or something that triggers when a new player joins the server, then I can just put every value from the map into the array