How to sort users by latest post in mongoose,nodejs database?

Question

MongoDB

There are 2 collections.

messanges
authorId
to (to whom - I always admin)
createdAt
text

users
_id
avatarURL
name

using mongoose.

The task on sense costs like simple.
Sort the list of users who wrote last, and give information about them.
1. I sorted the posts by date to see the latest posts

2. I grouped the users by their ID to remove duplicates - thus getting a list of users
who wrote last.
3. since I didn’t manage to somehow Join (populate) in the code, I twisted information about users in a loop.
4. Whether it is possible to display the last message from sorting in the same request, otherwise I have to send the request to the database again.
Is my logic of selecting and sorting from the database correct - because sometimes it sorts messages in different ways.

How can I competently make a choice all the time with the help of aggregate, choice and join?
(I could not do any lookup - it seems the information is simple)

There may be idiotic code - I write on nodejs not so long ago

сonst mess = await Message
    .aggregate(
    [
        { "$match": { "to": 'admin'  } },
        { "$sort": { "createdAt" : 1 } },
    { "$group": {"_id": {"authorId": "$authorId",}}}
  
    ])
  
  //SEARCH USER BY MESS ID AFTER SORT
    let allusers = new Array();
    let n=0;
    for (const item of mess) {  
        users0 = await Users.find({_id: item._id.authorId});
    allusers.push(users0.map(u => u.toDTO()));
    
  }

res.render('_ajax/messanges', {messusers: allusers})

I tried like this but distinct and sort don't work together

messusers =  await Message
.find({to: 'admin'})
.sort({createdAt: 'asc'})
.distinct('authorId')
.populate({ path: 'authorId', select: 'avatarURL name' })

Answer 1

something along the lines of:

.aggregate(
    [
        { "$match": { "to": 'admin'  } },    
    { "$group": {_id: "$authorId", "createdAt": {$max: "$cretedAt"}},
      {$lookup: {
 {
         from: "user",
         localField: "_id",
         foreignField: "_id",
         as: "user"
       }
        { "$sort": { "createdAt" : 1 } },
},
    ])