Hi ,
Every single component of GameSparks’ SDK is compatible with Unreal Engine 4’s network layer except The Real-Time SDK because they both do the same thing, send information to other clients for them to replicate it.
Matchmaking, Challenges (Game Lobbies), Leaderboards, downloadables, achievements, virtual goods and all those configurable backend components have no quarrel with UE4 or it’s network layer.
GameSparks is a socket based system. When the game is on, a session is active between client and backend. Data is passed through and used with requests (Calls/functions) that trigger responses. You can also receive messages that are broken down and used by listeners. None of this interrupts unreal or it’s networking layer. In fact they work very well together.
Hope that helps. If you want to know more or have any further questions please head to the GameSparks forums where one of the team can jump in quickly and help you out directly.