This is not completely related to nim, but have you tried a google search first? I found some interesting threads on the subject:
[https://gamedev.stackexchange.com/questions/117602/updating-a-multithreaded-entity-component-system](https://gamedev.stackexchange.com/questions/117602/updating-a-multithreaded-entity-component-system) [https://gamedev.stackexchange.com/questions/62748/using-an-entity-system-architecture-with-task-based-parallelism](https://gamedev.stackexchange.com/questions/62748/using-an-entity-system-architecture-with-task-based-parallelism) [http://t-machine.org/index.php/2015/05/02/data-structures-for-entity-systems-multi-threading-and-networking](http://t-machine.org/index.php/2015/05/02/data-structures-for-entity-systems-multi-threading-and-networking)/ But i'd say that, unless you have some experience making games and know what the purpouse of this engine will be (why not tailor one for your own needs instead of trying to fit your game into a generic engine?) thinking before hand will not give you too much experience. First try to make some game with only one thread and take notes on how would you parallelize that.
