1. Introduction: Why Small Indentation Mistakes Break Everything You are configuring a server using a configuration file. The file looks correct to you. But when you restart the service, it crashes with a cryptic error. The entire application goes down because of one tiny mistake that is invisible to the human eye. You are writing infrastructure-as-code using a popular orchestration platform. You copy-paste an example from the internet, make a few edits, and deploy it. The system silently fails—not with a red error message, but with nothing. Your containers do not start. Your services do not respond. You are setting up continuous integration for your software project. You write a pipeline configuration file. Everything looks right. But the pipeline hangs indefinitely or skips critical steps because a single space is in the wrong place. This is the frustrating world of YAML (YAML Ain't Markup Language). It is a human-friendly way to write configuration files. But it is also extremel...