Such a change may have a huge impact on the internal state of the language server. But on protocol side it's probably minor. You should just one relevant piece of the new state on the next Goto Definition / Auto completion / etc. request. No need to stream the whole new state from the language server to the client on each update.
My current estimation is that the protocol costs are O(1) regarding project size.
My current estimation is that the protocol costs are O(1) regarding project size.