I’m curious about the actual message passing implementation(s) here - there’s a lot of “CS passes a message to all the GSs” - what’s that look like? Is it a gen

I’m curious about the actual message passing implementation(s) here - there’s a lot of “CS passes a message to all the GSs” - what’s that look like? Is it a general pubsub system? Did they roll their own? What’s the actual machinery here?