I may not be up to speed on enhancements. I saw one thread about a possible future enhancement to Songkong to lift the throughput limitation for those of us running our own Musicbrainz Server. Will this change be made soon? I don't know the difficulties on the programming side.
That was an interesting comment about how a Musicbrainz Server will not really improve performance for Songkong due to this limitation. What is it, one song per second, or something like that?
That was fixed some time ago, when you start SongKong on the bottom left handside of the status bar there is a field that says MusicBrainz Delay, this shows how much additional delay SongKong inserts into webservice requests to abide by the one request per second limit.
If you have a Local MusicBrainz server configured on the Server tab and enabled with Use Local MusicBrainz Server then this delay should be zero and this is the time saved using local Musicbrainz server.
Of course requests to Discogs and Acoustid are still subject to the request limiting. You may want to consider disabling Update and Search from Dicogs on the Match tab for optimum performance.