db={"Address":[{"_id":ObjectId("64a67f2fdbe7c36e2e6c15c6"),"name":{"type":"permenant"},"address":"permenant address 1","parent":{"ref":"Parent","id":ObjectId("64a67f32dbe7c36e2e6c15c8")}},{"_id":ObjectId("64a67f2fdbe7c36e2e6c15c7"),"name":{"type":"secondary"},"address":"permenant address 2","parent":{"ref":"Parent","id":ObjectId("64a67f32dbe7c36e2e6c15c8")}},{"_id":ObjectId("64a67f2fdbe7c36e2e6c15c3"),"name":{"type":"other"},"address":"other address 2","parent":{"ref":"Parent","id":ObjectId("64a67f32dbe7c36e2e6c15c8")}}],"Parent":[{"_id":ObjectId("64a67f32dbe7c36e2e6c15c8"),"name":{"user":"xyz"},"data":{"age":"55"}}]}

db.Address.aggregate([{$lookup:{from:"Parent",localField:"parent.id",foreignField:"_id",as:"parent"}},{$unwind:"$parent"},])