When the kingdom grows beyond a few castles, someone must decide where every banner flies. A single container is easy to understand. You package an application, start it, expose a port, and watch it run. Add a database, cache, and supporting service, and Docker Compose can organize the small caravan well enough for development and modest deployments. The trouble begins when that caravan becomes a kingdom. Once dozens or hundreds of containers must remain available across multiple machines, the difficult question is no longer how to start them. The difficult question becomes who keeps track of everything after you stop watching. Imagine a kingdom dotted with castles. Each needs guards,…