A question about phab:T108586: Does running Herald rules blocks every change to every task? Many rules should actually run asynchronously ("as a job").
Topic on Talk:Phabricator/Help
Yes, Herald is synchronous (hence why we discourage new/more complex Herald rules). There's no such thing as asynchronous "jobs" in Phabricator, that's a MediaWiki concept.
So it may be meaningful to ask upstream to allow running some Herald rules asynchronously. This will optimize performance significantly, giving the low transaction rate (=frequency of actions) in Phabricator.
No, that's not a plausible request and I would not endorse it.