How to store continuous scale data in a database

I have a very simple Node.js server (using Express.js) running locally on port 8000.

Using the npm package serialport, I managed to connect to a scale and get its weight in a continuously mode like so.

Terminal output..

0
10
20
30
50
50 stable
50 stable
...

I want to save the scale stable weight to a database (in my case MongoDB Atlas), but I don't want to make hundreds of requests as the scale weight changes.

I know tools like RxJS and one of its operators distictUntilChange, but I'm not using any client.

How this can be done working only with a server?

Since you haven't shown any code, here's a conceptual answer, which assumes that your readings are coming from an async iterator and that you already have a function for uploading each weight value. In this example, the weight property of each reading is a number and the stable property of each reading is a nullish boolean.

async function uploadLoop (scaleReaderIterator, uploadWeight) {
  let previousWeight;

  for await (const {weight, stable} of scaleReaderIterator) {
    if (
      !stable || // the weight reading isn't stable, OR
      weight === previousWeight // the weight hasn't changed since last time
    ) continue; // don't do anything else in this code block
    // else

    // update the previous value
    previousWeight = weight;
    // upload it
    uploadWeight(weight);
  } // loop
}