HashiCorp infrastructure-as-code tool used in the talk as a best-practice example of separating DAG definition from node execution: HCL/state describes the DAG (e.g. `aws_s3_bucket_logging` depending on `aws_s3_bucket`), provider modules written in Go contain the imperative code that calls AWS APIs to create the resources. The Terraform state file is 'a DAG frozen with the execution results' (ARNs, names etc.).