What if you could build serverless applications that cold-start in under a millisecond, run anywhere—from your laptop to Kubernetes to the edge—and require no changes to move between environments? This session introduces Spin, a CNCF open-source WebAssembly (Wasm) developer toolkit designed for performance, portability, and simplicity. Attendees will learn how to build a Spin app, write polyglot WebAssembly functions with sub-millisecond cold starts, and run them locally using the Spin CLI. The same app will then be deployed to Azure Kubernetes Service with SpinKube, the open-source Spin runtime for Kubernetes, and to Fermyon Wasm Functions, Akamai’s multi-tenant, globally distributed PaaS—all without rewriting or cross-compilation. The session teaches how WebAssembly and Spin enable true portability across the compute continuum, letting developers build once and run anywhere with no vendor lock-in. This tutorial demonstrates how Spin is reshaping what serverless can be.