By general service do you mean a system where response time isn't especially important? Using TCP to fan-out messages in a PubSub pattern is going to waste netw

By general service do you mean a system where response time isn't especially important? Using TCP to fan-out messages in a PubSub pattern is going to waste network and compute resources in a serious way. It can easily exhaust capacity or result in convoluted, unreliable systems with layers of proxies for managing load. FWIW when you talk about different requirements, I'm not sure you're correct. For traders, sure, oftentimes they can just dump old data if they fall behind because it's mostly irrelevant. However, stock exchanges have performance and reliability/availability as top requirements. They must record all transactions and can't crash or lock-up. Most use multicast internally and externally. They would never be able to scale and maintain a low response time with TCP.