Does Fastify Work With Fly.io?
Fastify works excellently on Fly.io with minimal configuration, leveraging Fastify's performance to serve users globally with Fly's edge deployment model.
Quick Facts
How Fastify Works With Fly.io
Fastify runs natively on Fly.io without any special modifications. Fly.io's Docker-based deployment process treats Fastify like any Node.js application, making it straightforward to containerize and deploy. The combination is particularly effective because Fastify's low overhead and fast request handling align perfectly with Fly.io's distributed infrastructure—your app starts quickly in edge regions and handles traffic efficiently.
The typical workflow involves creating a Dockerfile, setting your Node.js app to listen on the port Fly assigns (usually via PORT environment variable), and deploying with `fly deploy`. Fastify's built-in health check capabilities integrate seamlessly with Fly's health monitoring. For edge-to-origin communication, you can leverage Fly's private networking to connect to databases or other services, while Fastify's async/await pattern and connection pooling handle concurrent requests efficiently across distributed regions.
One architectural advantage: Fastify's plugin system allows you to conditionally load middleware based on the deployment environment, making it simple to add Fly-specific features like graceful shutdown handling or region-aware routing without bloating your codebase.
Best Use Cases
Quick Setup
npm init -y && npm install fastifyimport Fastify from 'fastify';
const fastify = Fastify({
logger: true,
});
fastify.get('/health', async () => ({
status: 'ok',
timestamp: new Date().toISOString(),
}));
fastify.get('/api/hello', async (request, reply) => ({
message: 'Hello from Fly.io!',
region: process.env.FLY_REGION || 'unknown',
}));
const port = parseInt(process.env.PORT || '3000', 10);
await fastify.listen({ port, host: '0.0.0.0' });
console.log(`Server running on port ${port}`);Known Issues & Gotchas
Fastify listens on 0.0.0.0 by default but Fly requires explicit port binding via environment variable
Fix: Use `const port = process.env.PORT || 3000` when calling `fastify.listen()` and ensure your fly.toml specifies the correct internal port
File uploads and temporary storage don't persist across deployments or multiple instances without external storage
Fix: Use Fly's persistent volumes for stateful data, or integrate S3-compatible storage (e.g., Tigris) for uploads
Cold start times can be noticeable in distant regions if your app has heavy dependencies or slow initialization
Fix: Lazy-load plugins, minimize bundle size, and consider keeping instances warm with scheduler jobs
Environment variables must be set via `fly secrets set` or in fly.toml, not hardcoded in code
Fix: Use `process.env.VAR_NAME` throughout and document required environment variables in your deploy checklist
Alternatives
- •Express.js with Fly.io—more mature ecosystem but heavier overhead than Fastify
- •Remix/Next.js on Fly.io—full-stack frameworks with built-in server rendering, better for hybrid applications
- •Deno with Fly.io—modern runtime with native TypeScript, alternative to Node.js if you prefer that ecosystem
Resources
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