At the time of writing, Pulumi is still kind of a new kid on the block. Most people have used some flavor of infrastructure as code (IaC) tooling. Terraform as the most common cross-cloud solution, or a cloud-focused one like specific tooling around CloudFormation (like troposphere, or CDK). Pulumi’s main selling point vs Terraform is, that you can code it in a language you already know - TypeScript and Python for example, instead of Terraform’s HCL.
