Hey VasyaCullin,
Just wanted to check and see what kind of large world multiplayer? Kind of like an MMO? Sweeney has addressed the MMO issue is a previous post: Atlas MMO Framework? - Feedback & Requests - Epic Developer Community Forums
I have also just located this video that may help you out with your question as well: World Browser Overview (Open World/ World Streaming experimental tool) - Community & Industry Discussion - Epic Developer Community Forums
Let me know if this is what you are looking for. Thanks and have a great day!