An API (Application Programming Interface) is crucial when considering cloud platform purchases. Cloud-native applications should be composed of the best components available to meet their needs. When making decisions about how to compose a solution, it's important to consider not only current requirements but also future growth and evolution. Choosing cloud services with APIs allows for seamless integration between different platforms and ensures that new components can be added without compatibility issues. This is similar to buying devices with standard ports and connectors, allowing users to replace or add components without needing to change the entire setup.