db={"courses":[{"_id":1,"createdBy":ObjectId("60f6ae1733257a3bcfe581e7"),"_shareWithUsers":ObjectId("60f6ae1733257a3bcfe581e7")},{"_id":2,"createdBy":ObjectId("60f6ae1733257a3bcfe581e7"),"_shareWithUsers":ObjectId("60f6ae1733257a3bcfe581e7")}],"courseassets":[{"_id":1,"_courseId":1,"createdBy":"Tom"," _assetId":"123"},{"_id":2,"_courseId":1,"createdBy":"Tom"," _assetId":"456"},{"_id":3,"_courseId":2,"createdBy":"Sam"," _assetId":"789"},{"_id":4,"_courseId":3,"createdBy":"Bob"," _assetId":"000"}]}

db.courses.aggregate([{"$match":{$or:[{createdBy:{$eq:ObjectId("60f6ae1733257a3bcfe581e7")}},{_shareWithUsers:ObjectId("60f6ae1733257a3bcfe581e7")}]}},{"$lookup":{"from":"courseassets","localField":"_id","foreignField":"_courseId","as":"docs"}},{"$unwind":"$docs"},{"$replaceWith":"$docs"}])