If the server caps how much it sends per connection and sends the nearest things first, a connection with a low cap gets distant NPCs late or not at all.
Why In crowded places, the server sends in order of importance within each connection’s send cap → Effect A connection with a low bandwidth estimate (e.g., a background window that’s slow to acknowledge) keeps pushing back entities further down the list → On screen Distant NPCs appear late or not at all on one side only
Primary owner Game team (Server development) · Also Game team (Client development)
Game team action items
Server: raise the priority of deferred entities the longer they wait (prevent starvation), guarantee a minimum update interval. Client: send acknowledgments on time even in the background so the bandwidth estimate doesn’t drop.
On the graph
Rises with load · Deferred entities per connection, bytes sent per connection
Where to look
Server-side, per connection: bytes sent per tick, send cap (estimated bandwidth), entities deferred for lack of room, and time since each entity was last sent. In Unreal, Networking Insights shows packet sizes per connection and the replicated objects inside them
Confirmed if
The invisible NPC is an entity deferred for a long time on that connection, that connection’s cap is lower than the others’, and deferred entities grow as it gets more crowded
Ruled out if
Nothing deferred and that NPC was sent on time: a stage after sending (receive buffer, loading, display settings). Every connection is at its cap: a server-wide send volume or AOI design problem
Check with
Game server or client logs and metrics
Sources
Actor Priority in Unreal EngineEpic Games When bandwidth is saturated, actors to replicate are chosen by priority (distance, line of sight, time since last replication); not every actor is replicated every time
State SynchronizationGaffer On Games Priority accumulation: entities that didn’t fit in this packet go first in the next one, and the bandwidth limit is adjusted in real time
Networking Insights in Unreal EngineEpic Games Shows the size of packets sent and received per connection and the replicated objects and properties inside them