Database
db={"chatMessages":[{"_id":1,"userId":1,"msg":12,"createdAt":ISODate("2022-01-22T11:00:33Z")},],"User":[{"_id":1,"sku":"almonds","description":"product 1","instock":120},]}
Query
db.chatMessages.aggregate([{$match:{_id:1}},{$sort:{createdAt:-1}},{$lookup:{from:"User",localField:"userId",foreignField:"_id",as:"user",},},{$unwind:"$user"},{$skip:0},{$limit:1},{$sort:{createdAt:1}},])