httpcat | simple utility for constructing raw HTTP requests | Command Line Interface library

I think that the use of forkJoin together with shareReplay does not cause any memory leak issue. The reason is the following:

• forkJoin notifies when all the Observables passed in as parameters complete. In this case, since the Observable passed to forkJoin are related to http calls, they complete just after the http call returns. therefore as soon as both http calls return, the Observable created by forkJoin notifies and then completes.
• The effect of shareReplay is to create an internal cache that makes sure that any subscription will get the last value notified by upstream. In this case, the last value notified by upstream is the only value notified by the Observable created by forkJoin

The risk of memory leaks or, at least, the risk of uncontrolled execution of code with shareRepley comes when the source Observable is an infinite stream (for instance a stream created with interval). In this case, shareReplay creates an Observable which never completes, even if there are no subscribers, unless the refCount property of ShareReplayConfig is set to true.

This behavior is explained in details in the documentation.

In any case this is not a risk you run, since the source Observable you have will emit only once and then complete.