Use web-sockets .. So, that the client doesn't needs to worry about the changes in data at server end. The server will auto-push the changes to client whenever their is any change.

Meteor has such a world class implementation of same functionality out of the box.

There are number web-socket modules for Angular . github.com/AngularClass/angular-websocket . On server-end web-sockets are supported by almost all languages natively.

Your API could use SSE (Server Sent Event). It's an open connection that keeps sending data over.

I don't know about Angular or RxJS, but there is EventSource:

const client = new EventSource('/endpoint')
client.onmessage = ev => {
  console.log(ev.data)
}

You can also use the fetch response body .getReader() and work with the readable stream.