Mongoose delete records after certain time - node.js

Question

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 1

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();