db={"Test1":[{"_id":"kcXtyaB7jGPw9Ks","dateCreated":"2022-07-12T13:09:16.270Z","dateModified":"2022-07-12T13:09:16.270Z","data1":1,"data2":100,"data3":5,"createdBy":"xQQrzRgi8","updatedBy":"56sgAeKfx"}],"Test2":[{_id:"xQQrzRgi8",fullName:"test name created"},{_id:"56sgAeKfx",fullName:"test name update"}]}

db.Test1.aggregate([{"$lookup":{"from":"Test2","localField":"updatedBy","foreignField":"_id","as":"result"}},{"$set":{"updatedBy":{"$first":"$result.fullName"}}},{"$lookup":{"from":"Test2","localField":"createdBy","foreignField":"_id","as":"result"}},{"$set":{"createdBy":{"$first":"$result.fullName"}}},{"$project":{"result":0}}])