What is the Replication Graph?
The Replication Graph is Unreal Engine's system for managing network relevancy at scale. Instead of iterating over all actors for each connection every frame, it organizes actors into spatial and logical groups that can be evaluated more efficiently.
This becomes critical when your game has thousands of replicated actors — the default relevancy checks simply can't keep up.
The Node Architecture
At its core, the Replication Graph is built on a node hierarchy. Each UReplicationGraphNode is responsible for a group of actors.
class UReplicationGraphNode : public UObject
{
virtual void GatherActorListsForConnection(
const FConnectionGatherActorListParameters& Params
);
TArray<UReplicationGraphNode*> ChildNodes;
};The key insight is that nodes can short-circuit evaluation — if a spatial node determines a connection is too far away, it skips all child nodes entirely.
"The Replication Graph was built for Fortnite's Battle Royale mode, where 100 players and thousands of actors made the old system untenable."
Performance Impact
In our testing with a 64-player scenario and 3,200 replicated actors, the Replication Graph reduced server-side replication CPU time by approximately 78%.
- Default relevancy: ~4.2ms per frame
- Replication Graph (spatial only): ~1.1ms per frame
- Replication Graph (spatial + always relevant): ~0.9ms per frame