Introducing Halcyon Edge Runtime

Today we're announcing Halcyon Edge Runtime -- a lightweight, V8-based execution environment designed for deploying server-side JavaScript and TypeScript to the edge. Your code runs in 280+ locations worldwide, with cold starts under 50ms and automatic scaling to zero.

We've been running this in beta with 200+ teams for the past four months, and the results have exceeded our expectations. Edge Runtime now powers over 3 billion requests per month across our customer base.

Why We Built This

Existing edge runtimes force a choice: compatibility or performance. You either get a full Node.js environment with 500ms+ cold starts, or a stripped-down runtime that breaks half your dependencies. We wanted both: broad Web API compatibility with sub-50ms cold starts.

Edge Runtime achieves this through V8 isolate snapshots (see our cold starts deep-dive), a custom module loader that eliminates redundant parsing, and a compatibility layer that implements 94% of the Web Platform APIs that matter for server-side code.

Key Features

• Sub-50ms cold starts. V8 heap snapshots, pre-warmed isolate pools, and predictive warming combine to keep latency imperceptible.
• 280+ edge locations. Your code runs within 50ms of 95% of the world's internet-connected population.
• Web-standard APIs. Fetch, Streams, Crypto, URL, TextEncoder/Decoder, Cache API, and more -- all implemented natively.
• TypeScript-first. Write TypeScript directly. No build step required. We handle transpilation at deploy time and cache the result.
• Scale to zero. You don't pay for idle. When traffic stops, your isolates are reclaimed. When it returns, you're back in under 50ms.
• Built-in KV and Durable Objects. Persistent state at the edge, without managing infrastructure. Key-value storage for simple lookups, Durable Objects for coordination and stateful logic.

Getting Started

Deploy your first edge function in under a minute:

// halcyon.config.ts
import { defineConfig } from "halcyon";

export default defineConfig({
  name: "my-api",
  routes: [
    {
      path: "/hello",
      handler: "./src/hello.ts"
    }
  ]
});

// src/hello.ts
export default {
  async fetch(request: Request): Promise<Response> {
    const geo = request.cf?.city ?? "somewhere";
    return new Response(
      JSON.stringify({ message: `Hello from ${geo}!` }),
      { headers: { "Content-Type": "application/json" } }
    );
  }
};

Then deploy with a single command:

# Install the CLI
npm install -g halcyon

# Deploy to 280+ edge locations
halcyon deploy

  Deploying my-api...
  Snapshot created (2.1 MB)
  Deployed to 284 locations in 1.8s
  https://my-api.halcyon.run

Edge Runtime is available today on all plans, including the free tier. Check the documentation to get started, or jump into our Discord if you have questions.