Exactly! And the reason for that is because it uses JSII to convert TypeScript to other languages. And JSII doesn’t understand any complex types. So CDK author

Exactly! And the reason for that is because it uses JSII to convert TypeScript to other languages. And JSII doesn’t understand any complex types. So CDK authors are forced to use very basic primitives. Which doesn’t take away anything from its quality in the end. CDK project uses types that were probably supported in TypeScript v1.0.