In my [previous post]({{ site.baseurl }}{% post_url 2018-03-26-rxjs-combinelatest-startwith %}) I came across a quirk with Angular, Observables and the Async pipe. That is, each subscription to an observable will initiate the observables execution. Hence we were calling the api once per async subscription. A subscribe call is simply a way to start an “Observable execution” and deliver values or events to an Observer of that execution.http://reactivex.io Original version <p>{{ (result$ | async).