Multithreading in further giant MMO worlds

How is a gameworld of tremendous giant dimension dealt with? I used to be at all times questioning how video games deal with giant MMO worlds. Till now I believed that separation of areas was the important thing for video games like World of Warcraft. In WoW there are continents, which are dealt with by totally different threads. And every continent may be multiphased and every section could be dealt with by totally different thread. However not too long ago I began taking part in a recreation referred to as Twin Universe. This recreation includes a single shard house of dimension greater than 100 000km x 100 000km x 100 000km. There isn’t any loading when shifting round and you may be anyplace along with your 2m tall character and construct something of even smaller dimension. So, how is that this doable? Do they only have one core to course of this complete recreation world? (in fact use totally different threads for networking, consumer enter validation, database, and many others) Or did they provide you with a way how you can break up recreation world into zones and deal with each by totally different thread after which do some syncing and handovers when one thing occurs close to the zone edges? I at all times thought that that is inconceivable, as a result of all MMOs do some sort of world splitting like continents/planets/photo voltaic programs/realms.