Build serverless applications out of fast, portable WebAssembly components — and run them anywhere in milliseconds.

Welcome to Spin: Serverless WebAssembly Applications.

Spin is an open-source framework, originally created at Fermyon and now a CNCF project, for building and running event-driven serverless applications compiled to WebAssembly. Instead of packaging your code into a container that must be kept warm to stay responsive, Spin lets you write small components that compile to a portable .wasm binary, declare in a single spin.toml manifest which events should invoke them, and run with cold starts measured in milliseconds. This book follows that idea from the ground up. It opens with the cold-start problem that motivates the whole design, then explains the WebAssembly foundations — WASI and the Component Model — that make language-neutral, sandboxed components possible. From there it works through the manifest, components and triggers, writing apps in Rust, Go, JavaScript, and Python, the built-in key-value and SQLite stores, the spin CLI and its development loop, and packaging applications as OCI artifacts to run on Kubernetes with SpinKube. A closing chapter steps back to look at best practices, the ecosystem, and where Spin fits in the cloud-native landscape.

This title is part of the ShriIra library and is free to read in full, right here — our small contribution to making world-class knowledge easy to reach.

A note on reading it: open the Contents menu at the top of the reader to jump between chapters, use the Aa menu to set a comfortable text size, theme (light, sepia, or night), and single- or two-page layout. Your place is saved automatically, so you can always pick up where you left off.

We hope it serves you well.

— Shriira Press

Contents

1. Chapter 1 — The Cold-Start Problem
2. Chapter 2 — WebAssembly, WASI, and the Component Model
3. Chapter 3 — The Application Manifest
4. Chapter 4 — Components and Triggers
5. Chapter 5 — Writing Apps Across Languages
6. Chapter 6 — Built-in Storage and Services
7. Chapter 7 — The Spin CLI and Development Workflow
8. Chapter 8 — Packaging and Running on Kubernetes
9. Chapter 9 — Spin in Practice