Deploy Fastify

A Fastify server runs on Sevalla as an application: Nixpacks installs the dependencies from your Git repository, and the web process runs npm start, which starts Fastify on the port that Sevalla sets in the PORT environment variable.

Before you begin

A Sevalla company with a payment method, and a GitHub, GitLab or Bitbucket account for the repository. See Git providers.
Node.js 24 or later on your computer.

Create the project

Create a folder and install Fastify:

mkdir storefront && cd storefront
npm init -y
npm install fastify

Create the server:

server.js

import Fastify from "fastify";

const fastify = Fastify({ logger: true });

fastify.get("/", async () => {
  return { message: "Hello from Fastify on Sevalla" };
});

await fastify.listen({
  port: Number(process.env.PORT) || 3000,
  host: "0.0.0.0",
});

Keep installed packages out of the repository:

.gitignore

node_modules/

Prepare the project for Sevalla

Set the module type, the start script and the Node.js version in package.json:

npm pkg set type=module scripts.start="node server.js" engines.node="24.x"

Field	Why Sevalla needs it
`"type": "module"`	Lets `server.js` use `import` and top-level `await`.
`scripts.start`	Nixpacks, the default build strategy, starts the web process with `npm run start`.
`engines.node`	Nixpacks installs Node.js 24 instead of its default, Node.js 18. See Pin the Node.js version.

The listen() call matters most:

port comes from PORT, which Sevalla sets to the web process’s port (8080 by default).
host: "0.0.0.0" makes Fastify accept connections on all network interfaces. Fastify listens only on localhost by default, where Sevalla’s traffic can’t reach it.

Run npm start and open http://localhost:3000 to check the server locally. Then commit everything and push it to your Git provider:

git init
git add .
git commit -m "Prepare for Sevalla"
git branch -M main
git remote add origin https://github.com/acme/storefront.git
git push -u origin main

Deploy to Sevalla

Create the application

In the sidebar, click Applications, then click Create > Application. Under Source, click Private repository, then choose the Git provider, the Repository and the Branch. Under Location, choose a Data center. Keep the Size at H1 or choose a larger one, then click Create application. The application opens on its Overview tab with the status Not deployed yet: creating an application doesn’t deploy it.

Deploy

Click the Overview tab, then click Deploy now under Recent deployments. Check the Branch and click Deploy.

Turn on auto-deploy

To deploy every push to the branch automatically, click the Settings tab, then click Update auto-deploy in the Auto-deploy section. Turn on Auto-deploy and click Update auto-deploy. See Deployments.

Verify the deployment

On the Deployments tab, wait for the deployment’s status to change to Deployed. The application’s status next to its name changes to Running.
Click the domain under the application’s name, for example storefront-x7k2m.sevalla.app. The page shows {"message":"Hello from Fastify on Sevalla"}.

The application header with its name, Running status, repository, branch and the domain that opens the application

If the deployment fails, open it on the Deployments tab and read its build log, then see Troubleshoot builds and deployments. If it deploys but the domain doesn’t respond, check that listen() uses host: "0.0.0.0" and read the application’s runtime logs: Fastify’s logger prints the address it listens on.

Deploy changes

With Auto-deploy on, every push to the branch starts a deployment; otherwise, click Deploy now for each change. Each deployment builds the image, then replaces the web process’s instances. See Deployments.

Add a custom domain

To serve the application from your own domain, such as shop.example.com, add the domain on the application’s Domains tab and create the DNS records that Sevalla shows. Custom domains need a web process larger than H1, so scale the web process first. See Custom domains.

Connect a database

Create a database in the same location as the application, then connect the application to it with Add environment variables to the application turned on. Sevalla adds DB_URL, DB_HOST, DB_PORT, DB_DATABASE, DB_USERNAME and DB_PASSWORD to the application (what each one holds), and they apply at the next deployment. Read them in the server with process.env.DB_URL.

Migrate

JavaScript

Python

Before you begin

Create the project

Prepare the project for Sevalla

Deploy to Sevalla

Verify the deployment

Deploy changes

Add a custom domain

Connect a database

​Before you begin

​Create the project

​Prepare the project for Sevalla

​Deploy to Sevalla

​Verify the deployment

​Deploy changes

​Add a custom domain

​Connect a database

Before you begin

Create the project

Prepare the project for Sevalla

Deploy to Sevalla

Verify the deployment

Deploy changes

Add a custom domain

Connect a database