I recently came across the awesome folks over at Heroic Labs who are making a open-source server called Nakama which can be used for social and realtime games. It is cloud agnostic as well as open source under the Apache 2.0 license. So you can run it on Amazon EC2, Google Servers, etc. with no lock in from the software side. It can be used to make things from social games to MOBAs to MMOs.
They are currently making a UE4 integration for Nakama - However they need input / feedback from the Unreal Engine community for how the C++ side of the API should be structured. If anyone wants to help out with this join the gitter linked below.
You can find out more at -