MongoDB document insertion and referencing
Why not put it all in the same document? You could also put it in a different collection. One way or another since you don't have any schemas to update, just try whatever suits your case. If this is a many to many relationship (like films-actors) then embedding everything wouldn't really work. You would have to reference other documents.

Film Collection:
    {
      {
          film1: ....
          actors: [actor_ids]
      },
      etc...
    }

Actor Collection:
{
     {  
          actor1:....
          actor_id: objectId
      },
     etc...
}


https://docs.mongodb.com/manual/core/data-model-design/