How to synchronise a distributed pubsub system

Building a fully distributed system is really hard. But a few compromises can go a long way. Hear how Paddy CTO and Co-Founder of Ably, would white board out complex problems and where needed centralise small pieces in a single region. It might seem simple or small but trade offs like this can go along way and still meets the requirement of a pier to pier region relationship where any region can fail and come back online at anytime. What trade offs are hidden in your architecture that would simplify your stack?