db={"Product":[{id:"1",model:"Light1",category:"Light"},{id:"2",model:"Light3",category:"Light"},{id:"3",model:"Lock1",category:"Lock"}],"Item":[{id:"1",model:"Light1",category:"Light",color:"Blue"},{id:"2",model:"Light2",category:"Light",color:"Blue"},{id:"3",model:"Lock1",category:"Lock",color:"Blue"},{id:"4",model:"Light3",category:"Light",color:"Blue"},{id:"5",model:"Lock2",category:"Lock",color:"Blue"}]}

db.Item.aggregate([{"$lookup":{"from":"Product","let":{"model":"$model","category":"$category"},"pipeline":[{"$match":{"$and":[{"$expr":{"$eq":["$model","$$model"]}},{"$expr":{"$eq":["$category","$$category"]}}]}}],"as":"result"}},{"$match":{"result":{"$ne":[]}}},{"$project":{"_id":0,"result":0}}])