Pulumi is an infrastructure-as-code platform that lets developers provision and manage cloud resources using general-purpose programming languages rather than a dedicated configuration syntax. The Pulumi documentation describes it as an “open source platform for building, deploying, and managing cloud infrastructure using your favorite programming languages.” The project’s source repository on GitHub frames it more pointedly as “the easiest way to build and deploy infrastructure, of any architecture and on any cloud, using programming languages that you already know and love.”
The defining choice that set Pulumi apart from earlier tools was its rejection of a custom domain-specific language. Where Terraform introduced its own HCL configuration language and CloudFormation used JSON or YAML templates, Pulumi reuses real programming languages. The project supports JavaScript and TypeScript on the Node.js runtime, Python, Go, the .NET languages (C#, F#, and VB.NET), and a YAML option for those who want it. The GitHub README pitches this directly: “Skip the YAML, and use standard language features like loops, functions, classes, and package management.”
Using a real programming language means infrastructure definitions can leverage abstractions that template languages handle awkwardly or not at all. Loops, conditionals, functions, classes, and the language’s native package manager all become available for describing infrastructure, and the same IDEs, test frameworks, and refactoring tools used for application code apply to the infrastructure code as well. Pulumi works across AWS, Azure, Google Cloud, Kubernetes, and many hundreds of additional providers.
Despite using imperative-looking host languages, Pulumi remains fundamentally declarative under the hood: the program builds up a desired-state model that the engine then reconciles against existing infrastructure, computing and previewing a plan before applying changes. This mirrors the plan-and-apply workflow that the broader infrastructure-as-code category had established. Pulumi was founded by Joe Duffy and a team of former Microsoft engineers, and its general availability in 2018 marked a notable alternative branch in how teams express infrastructure as code.