The Worker model, pioneered by CloudFlare and others, provides a lightweight, secure way of running serverless workloads. WebAssembly (Wasm) is a portable binary format that allows code from a variety of languages like Rust, JavaScript, and Python.

This talk introduces runwasi, an open-source library to develop containerd shims that leverage WebAssembly and the WebAssembly System Interface (WASI). Together, Wasm and Runwasi enable deployment of secure, lightweight apps whenever you can run containers.

Thanks to the sandboxed execution environment, the workloads get an extra isolation layer. The capability-based security model that WASI follows ensures the functions only have access to the required resources. Application distribution is another challenge. Wasm modules are small and compact (20MB for a Python Wasm module).

This talk will provide some of the challenges involved and a practical demonstration of what it looks like to run a Wasm serverless app on top of Kubernetes.