db={users:[{name:"John",house_id:1,car_id:1},{name:"Charles",house_id:1},{name:"Jessy",house_id:2,car_id:2},{name:"Tim",house_id:3}],houses:[{_id:1,name:"house1"},{_id:2,name:"house2"},{_id:3,name:"house3"}],cars:[{_id:1,name:"car1"},{_id:2,name:"car2"}]}

db.users.aggregate([{$match:{name:"Charles"}},{"$lookup":{"from":"houses","as":"houses","localField":"house_id","foreignField":"_id"}},{"$lookup":{"from":"cars","as":"cars","localField":"car_id","foreignField":"_id"}},{$unwind:{path:"$cars",preserveNullAndEmptyArrays:true}},{$unwind:{path:"$houses",preserveNullAndEmptyArrays:true}}])