# Get started with Neon Functions

A function takes a request and returns a web response, running on long-lived Node.js compute next to your database. The request can come over HTTP, or from a [Function Trigger](/guides/neon-functions-triggers-overview) on a schedule or object upload.

## Hello world

Write a file and deploy it:

```typescript title="hello-world.ts"
export default {
  fetch: (request: Request) => new Response('Hello world'),
};
```

```bash title="Neon CLI"
neon link
neon functions deploy helloworld --src hello-world.ts
```

Done, function deployed. Get the public URL:

```bash title="Neon CLI"
neon functions get helloworld -o yaml
```

```yaml
id: helloworld
slug: helloworld
name: helloworld
invocation_url: https://br-wispy-brook-a1b2c3d4-helloworld.compute.c-2.us-east-2.aws.neon.tech/
current_deployment:
  id: 1
  status: completed
  memory_mib: 2048
  runtime: nodejs24
  created_at: 2026-08-03T21:19:18.120982Z
active_deployment:
  id: 1
  status: completed
  memory_mib: 2048
  runtime: nodejs24
  created_at: 2026-08-03T21:19:18.120982Z
created_at: 2026-08-03T21:19:17.989227Z
```

When `status` is `completed`, the function is live. Call `invocation_url` to see the function's output, which is "Hello world" in this case.

That's a deployed function in three commands. The rest of this guide builds a more realistic one: declared in `neon.ts`, run locally with `neon dev`, and querying Postgres.

::::steps
:::step{title="Prerequisites"}
- A Neon project in AWS US East (Ohio) (`aws-us-east-2`), AWS US East (N. Virginia) (`aws-us-east-1`), AWS Europe (Frankfurt) (`aws-eu-central-1`), or AWS Asia Pacific (Singapore) (`aws-ap-southeast-1`). Support is expanding toward [all regions](/guides/manage-operate-introduction-regions).
- The latest `neon`, installed and authenticated. Functions commands are new and change often, so upgrade before you start (`npm install -g neon@latest`).
- Node.js 20 or later. Deployed functions run on Node.js 24, so use 24 locally for the closest match.

To give your AI coding assistant context for Neon and Functions, install the [agent skills](/guides/ai-agents-on-neon-ai-agent-skills) with the [Neon CLI](/guides/apis-sdks-cli):

```bash
neon skills -s neon -s neon-functions
```

Without the Neon CLI, run `npx skills add neondatabase/agent-skills -s neon -s neon-functions` instead.
:::

:::step{title="Set up your project"}
Create your project directory:

```bash
mkdir my-function && cd my-function
```

Then link the directory to your Neon project. There are two ways:

**With an AI coding assistant.** Ask your assistant to set up Neon for the project. Using the skills you installed, it links your project (creating one if you need it) with `neon link` and pulls your environment variables. Sign-in opens a browser window, so complete the OAuth step when prompted.

**By hand.** Run `neon link` and select your project and branch when prompted (or pass `--project-id`). This writes a `.neon` file and pulls the branch's environment variables into a local `.env` file (or `.env.local` if there's no `.env` yet).

```bash
neon link
```

To start from a working example instead, run `neon bootstrap`. It scaffolds a starter template, installs dependencies, and links it. Templates include a REST API, GraphQL API, tRPC API, MCP server, realtime chat and counter, AI agents, and Discord, Telegram, and WhatsApp bots. Run `neon bootstrap --list-templates` for the full catalog. This guide builds the function by hand.
:::

:::step{title="Define your function"}
Create `neon.ts` at your project root. It declares your functions and is what `neon dev` and `neon deploy` read:

```typescript title="neon.ts"
import { defineConfig } from "@neon/config/v1";

export default defineConfig({
  functions: {
    // The key is the function's slug:
    // a permanent ID used in CLI commands and the URL.
    hello: {
      name: "My first function", // display label only
      source: "./functions/hello.ts", // path to the handler file
    },
  },
});
```

The slug is permanent: it can't be renamed after the first deploy. See the [neon.ts reference](/guides/apis-sdks-reference-neon-ts) for all options.

Install dependencies:

```bash
npm install @neon/config @neon/functions hono pg
npm install --save-dev @types/pg
```

A function is any module whose default export has a `fetch(request)` method that returns a `Response`. That can be an object with a `fetch` method:

```typescript
export default {
  fetch: (request: Request) => new Response('Hello world'),
};
```

Or a bare async function:

```typescript
export default async function handler(request: Request) {
  return new Response('Hello world');
}
```

A Hono app exports the object shape, so `export default app` works directly. For this guide, write a handler that queries Postgres. `DATABASE_URL` is injected automatically from the linked branch's Postgres database:

```typescript title="functions/hello.ts"
import { Hono } from 'hono';
import { attachDatabasePool } from '@neon/functions';
import { Pool } from 'pg';

// Create the pool once at module scope so it's reused across requests.
const pool = new Pool({ connectionString: process.env.DATABASE_URL, max: 5 });
attachDatabasePool(pool);
const app = new Hono();

app.get('/', async (c) => {
  const { rows } = await pool.query('SELECT version()');
  return c.json(rows[0]);
});

export default app;
```

#### Use a connection pool, not the serverless driver

A function keeps running across requests, so connect to Postgres with a long-lived `pg` `Pool` created once at module scope. Don't use `@neondatabase/serverless` here: it's built for short-lived, edge-style invocations that open a connection per request, which wastes the persistent runtime a function gives you. Use the pooled `DATABASE_URL` for queries; use `DATABASE_URL_UNPOOLED` only where you need a dedicated connection (such as `LISTEN`/`NOTIFY`).

Call `attachDatabasePool(pool)` once after creating the pool (requires `@neon/functions` 0.8.0 or later). When Postgres drops an idle client (scale-to-zero, pooler reclaim, a TCP reset), `pg` emits an `error` on the pool; with no listener attached, that becomes an uncaught exception and the isolate exits. `attachDatabasePool` swallows expected idle disconnects and logs anything unexpected. The pool has already discarded the dead client, so the next query opens a fresh connection. You don't need to drain the pool on shutdown: when the runtime evicts an isolate, Neon's pooler reclaims those connections for you.
:::

:::step{title="Develop locally"}
`neon dev` serves all functions declared in `neon.ts` with hot reload. It injects `DATABASE_URL` and other Neon env vars from the linked branch. See [Environment variables](/guides/neon-functions-environment-variables) for the full list and how to pull them into a local `.env` file.

```bash
neon dev
```

The terminal prints the URL for each running function:

```
Neon Functions dev server

  hello                http://localhost:8787
```
:::

:::step{title="Deploy"}
`neon deploy` reads `neon.ts` and applies it to the linked branch, deploying every function it declares:

```bash
neon deploy
```

The CLI bundles each function with esbuild, uploads it, and waits for the deployment to complete.

To deploy a single file without a `neon.ts`, deploy it by slug instead:

```bash
neon functions deploy hello --src functions/hello.ts
```

For all deploy options, including the Neon API, see [Deploy and manage functions](/guides/neon-functions-deploy).
:::

:::step{title="Invoke"}
Once the deployment reaches `completed`, retrieve the invocation URL:

```bash
neon functions get hello
```

The `invocation_url` field contains the public URL for your function:

```
https://<branch_id>-<slug>.compute.<cell>.us-east-2.aws.neon.tech/
```

Call it with curl:

```bash
curl https://<branch_id>-hello.compute.<cell>.us-east-2.aws.neon.tech/
```

The response is a JSON object with your branch's Postgres version:

```json
{ "version": "PostgreSQL 17.x on ..., compiled by gcc ..." }
```
:::
::::

## Next steps

- [Function Triggers](/guides/neon-functions-triggers-overview): invoke a function on a cron schedule or an object upload instead of over HTTP
- [Deploy and manage](/guides/neon-functions-deploy): the CLI and API for managing deployed functions
- [Authentication](/guides/neon-functions-authentication): verify callers before a function runs
- [Custom domains](/guides/neon-functions-custom-domains): serve a function from a domain you own

## Need help?

Join our [Discord Server](https://neon.com/discord) to ask questions or see what others are doing with Neon. For paid plan support options, see [Support](/guides/postgres-introduction-support).

## Related pages

- [Add users and authentication](./auth-index.md)
- [AI tools for Agents](./ai-agents-on-neon-index.md)
- [APIs & SDKs](./apis-sdks-index.md)
- [Changelog](../changelog.md)
- [Explore the full platform: functions, object storage, AI Gateway, and more](./neon-docs-index.md)
- [Integrating with Neon](./building-on-neon-index.md)
- [Lakebase Postgres](./postgres-index.md)
- [More](./more-index.md)
- [Neon AI Gateway](./ai-gateway-index.md)
- [Neon community](./community-index.md)

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