Publish/Subscribe Events with Sugar?

Jeff Bickart ,

How is your publisher sending those events? realtime through streams? queueing technology? 

An event-driven architecture usually has a middleware (queue or streaming/kafka topics, etc) that will broadcast that message and usually can transform that to its consumers. 

I would leverage AWS SQS (or your architecture's middleware), consume it from there, and push it to Sugar through RestAPI.

under the covers, consumers are daemons that are listening for those events and PHP isn't a great fit for that.

Did you check the subscription targetlists in the campaign module? I used rhem many times for thag purpose.