Have you ever wondered how a geo-distributed app such as a Slack-like corporate messenger is architected and functions? How hundreds of microservices are deployed and communicate across distant geographies? How thousands of user messages and events flow in real-time across the countries? How are petabytes of data stored and accessed across continents? By taking a Slack-like corporate messenger as an example, we'll discuss the fundamental design principles for geo-distributed apps that are born to work across geographies.