Docker containers start in seconds. WebAssembly modules start in milliseconds. Spin makes building them as easy as Express.
What Is Spin?
Spin by Fermyon is a framework for building WebAssembly-based microservices. Write in Rust, Go, Python, JavaScript, or C# — compile to Wasm — deploy anywhere.
spin new -t http-rust my-app
cd my-app
spin build
spin up
# HTTP server running on http://localhost:3000
The Code
// Rust
use spin_sdk::http::{IntoResponse, Request, Response};
use spin_sdk::http_component;
#[http_component]
fn handle_request(req: Request) -> anyhow::Result<impl IntoResponse> {
Ok(Response::builder()
.status(200)
.header("content-type", "application/json")
.body(r#"{"message": "Hello from WebAssembly!"}"#)
.build())
}
// JavaScript/TypeScript
import { HandleRequest, HttpRequest, HttpResponse } from "@fermyon/spin-sdk"
export const handleRequest: HandleRequest = async function(request: HttpRequest): Promise<HttpResponse> {
return {
status: 200,
headers: { "content-type": "application/json" },
body: JSON.stringify({ message: "Hello from Wasm!" })
}
}
# Python
from spin_sdk.http import IncomingHandler, Request, Response
class IncomingHandler(IncomingHandler):
def handle_request(self, request: Request) -> Response:
return Response(200, {"content-type": "application/json"}, b'{"message": "Hello!"}')
Why WebAssembly Microservices
1. Cold start: <1ms — vs Docker 500ms-5s, Lambda 100ms-1s
2. Memory: 1-10MB — vs Docker container 50-500MB
3. Security — Wasm modules are sandboxed. No file system access, no network access unless explicitly granted.
4. Language agnostic — Rust, Go, Python, JS, C#, C++ → all compile to the same Wasm format
5. Portable — Wasm runs anywhere. No "works on my machine."
Key-Value Store
use spin_sdk::key_value::Store;
let store = Store::open_default()?;
store.set("user:123", b"Alice")?;
let name = store.get("user:123")?;
Deploy to Fermyon Cloud
spin cloud deploy
# Deployed in seconds. Global edge. Free tier.
Building microservices? Check out my developer tools or email [email protected].
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