Where Distributed Systems Complexity Comes From
Three machines in a rack are still three machines. They become a distributed system when they have to finish one job together, and that requirement is where the trouble starts. On a single machine you get three things for free. Every thread shares the same memory, so a write lands and everyone sees it. One clock puts every event in order. One lock protects the shared state. Move that job across a network and all three disappear. ...