db={orders:[{_id:ObjectId("65fee31937b6938d0107afe9"),products:[{_id:ObjectId("65fee0f137b6938d0107afe3"),qty:20},{_id:ObjectId("65fee0f137b6938d0107afe4"),qty:2}],uid:ObjectId("65fee0b337b6938d0107afe1")},{_id:ObjectId("65fee31937b6938d0107afea"),products:[{_id:ObjectId("65fee0f137b6938d0107afe2"),qty:4},{_id:ObjectId("65fee0f137b6938d0107afe4"),qty:1}],uid:ObjectId("65fee0b337b6938d0107afe0")}],users:[{_id:ObjectId("65fee0b337b6938d0107afe0"),name:"User 1",address:"Address 1"},{_id:ObjectId("65fee0b337b6938d0107afe1"),name:"User 2",address:"Address 2"}],products:[{_id:ObjectId("65fee0f137b6938d0107afe2"),name:"Product 1"},{_id:ObjectId("65fee0f137b6938d0107afe3"),name:"Product 2"},{_id:ObjectId("65fee0f137b6938d0107afe4"),name:"Product 3"}]}

db.users.aggregate([{$lookup:{from:"orders",localField:"_id",foreignField:"uid",as:"orders"}},{$lookup:{from:"products",localField:"orders.products._id",foreignField:"_id",as:"products"}}])