title: Listening for DB data changes in Angular using Rxjs or anything
body: <p>i have a Service in backend (node.js) i am subscribing it through the angular
  http client service and it is working fine. for my application more than one uers are there. <strong>so some other user can change the DB data . so whenever the changes happened to DB data i would like subscribe them immediately.</strong> so all users can view the consistent data i.e., data synchronized with DB data.
  i am using RXJS Observables in angular services.</p>