Mongoose delete records after certain time

I have a mongoose Schema which looks like this:

const USERS_DATA = new Schema({
    _id: Number,
    name: String,
    img: String,
    date: Date,
    phone: String,
    article: String,
    createdAt: {
        type: Date,
        required: true,
        default: Date.now,
        index: { expires: '3d' }
      }
},
{ 
    collection: "users",
    _id: false,
}

);

I need to push data to this schema.

const User = mongoose.model("users", USERS_DATA);
function pushToDB() {
    const newUser = new User({
      name: INPUT.name,
      img: INPUT.img,
      date: INPUT.date,
      phone: INPUT.phone,
      article: INPUT.article,
    });
    newUser.save(function (err) {
       mongoose.disconnect();
       if (err) return console.log(err);
});

}

This data have to be deleted after 3 days when it was pushed to database. How to implement it in node.js? I found it really confusing and tried lots of code. Any answers are appreciated! Thanks

P.S. I use mongoDb Atlas

Answer

You should separate the process to push the data into the database from the process to delete it after 3 days. You have already the first part :). For the second part, you can write a function deleteOldDocument. This function will query for documents in DB that are created for 3 days or more, and delete them. Then, you can run this function periodically, 1 time per day for example.

The pseudo-code, in case you need it :

async function deleteOldDocument() {

    const 3DaysAgo = ...; // here you can subtract 3 days from now to obtain the value
  
    // search for documents that are created from 3 days or more, using $lt operator
    const documentToDelete = await User.find({"created_at" : {$lt : 3DaysAgo }});

   // delete documents from database
   .....

   // recall the function after 1 days, you can change the frequence
   setTimeOut(async function() {
       await deleteOldDocument();
   }), 86400);    
}

// call deleteOldDocument to start the loop
deleteOldDocument();