faramir118/mangos — comment on commit 53ed5f371e887039902547ea680a1375219232e4
File:  line 0
By Undergarun:

For future implementation of cross realm battlegrounds / instances in a dedicated mangos-worldd execution, the best solution even if increase memory consumption is to make dtNavMesh per instance. IMHO make instances of the same map run on same thread is not the best way.

So: dtNavMesh locking vs dtNavMesh per instance are the possible scenarios for me.