Neon Functions

FIRST: Use the parent neon skill for a Neon overview, getting started with Neon, Neon development best practices, and more.

If the neon skill is not installed, fetch it from https://neon.com/docs/ai/skills/neon/SKILL.md or install it with:

neon skills -s neon -y

Neon Functions

This is a public beta feature, currently available in us-east-2 and eu-central-1.

Neon Functions are long-running Node.js HTTP handlers deployed onto a Neon branch. Each function gets a public HTTPS URL, runs in the same region as your database, and — if the branch has Postgres — gets DATABASE_URL injected automatically. You deploy and manage them through the same Neon CLI, neon.ts, and API you already use.

Use this skill to help the user define, run locally, deploy, and manage functions next to their database. Deliver a deployed function with its invocation URL, a working local neon dev loop, or a precise answer from the official Neon docs.

When to Use

Reach for Neon Functions when the workload is a request/response handler that benefits from staying alive and staying close to the data:

• Long-running request/response flows that outlast lambda-style limits. Agents that make several LLM calls and tool invocations per request, or image/video generation, routinely blow past the ~10–60s execution caps and short streaming windows of traditional serverless functions. Neon Functions are long-running: the handler just needs to _start_ responding within 15 minutes, and an open stream stays alive as long as bytes keep flowing. That's enough headroom for real agent workloads.
• Stateful streaming without bolting on Redis. Because a function stays alive across a request, it can host an SSE endpoint or a WebSocket server and hold the connection open in-process — no external state store (Redis, etc.) needed just to keep a stream coherent. Module-scope state (a pg pool, an in-memory counter) persists across requests on the same isolate.
• Compute that must sit next to Postgres. The function runs in the same region as the branch's database, so there are no cross-region round trips on every query. DATABASE_URL is injected for you.
• A backend that branches with your data. Each branch runs its own version of the function at its own URL, against its own isolated database (and storage, and gateway) state. Preview deployments, CI, and dev environments each get a self-contained backend — deploying to a child never affects the parent.
• Webhooks, bots, and post-response work. Webhook handlers that fan out into multiple DB writes, Discord/WebSocket bots, and fire-and-forget follow-ups via waitUntil (analytics, audit logs) all fit.
• Recurring HTTP work. A Function Trigger POSTs to the function on a cron (type: "schedule"). Same fetch handler, same 15-minute time-to-first-byte limit. See Function Triggers.

If the workload is a pure static site, or something that must run outside the supported regions (us-east-2, eu-central-1) today, this isn't the right tool yet (see Timeouts and Runtime Limits and Availability).

What It Does

• Long-running & serverless — Built for WebSocket servers (see WebSocket Servers), SSE endpoints (see Server-Sent Events (SSE)), long agent HTTP streams, and APIs. Still scales to zero when idle.
• Web-standard handler — A function is any default export with a fetch(request) method returning a Response (Workers/WinterTC-compatible). A Hono app exports exactly that shape, so export default app just works. Runs on Node.js 24, so all Node APIs are available.
• Close to your database — Runs in the branch's region; DATABASE_URL injected automatically when the branch has Postgres.
• Branchable — Each branch runs its own function version at its own URL against its own isolated state.
• Same CLI/API — Deploy and manage via neon, neon.ts, or the Neon API.
• Function Triggers — Neon POSTs to the function on a cron. See Function Triggers.

Availability

Check this precondition before setting anything up: Neon Functions is a public beta feature currently available in us-east-2 and eu-central-1. Confirm the user's Neon project is in one of these regions. Functions usage isn't billed during the public beta.

Architecture: Where Functions Fit

Neon (Functions included) is backend primitives, not full-stack app hosting. Host your app on Vercel (or Netlify, or another frontend/app host); Functions are the long-running, stateful slice of your backend that lives next to your data. They compose with that platform in two ways:

• Add a Function to a full-stack app. Your Next.js / TanStack Start app on Vercel (or Netlify) owns UI, auth (e.g. Neon Auth), and talks directly to Lakebase Postgres and Object Storage. When one workload outgrows the host's short serverless limits — a WebSocket or SSE server, or a long-running agent that would time out — move just that piece onto a Neon Function. (See Functions as an Agent Backend for the client-direct pattern.)
• Run the whole backend control plane on Functions. Especially when the frontend is client-only — TanStack Router, React Router in client mode, and similar SPAs hosted on Vercel or Netlify — the client calls Functions directly. Build REST APIs and request/response agents, host MCP servers, and run anything stateful or that belongs close to Postgres and Object Storage.

Either way, secure a Function like any standalone REST API: verify a JWT or API key at the top of the handler (see the WARNING under Functions as an Agent Backend). Because a Function is just your backend, you can move pieces between your host and Neon — relocate an agent or a stateful WebSocket server onto a Function when it needs more runtime, and back if needed.

Setup

Functions are declared in neon.ts (see the neon skill for the branch-first workflow and neon.ts basics). Add @neon/config and declare functions under preview.functions, keyed by slug:

// neon.ts
import { defineConfig } from "@neon/config/v1";

export default defineConfig({
  preview: {
    functions: {
      todos: {
        // slug: ^[a-z0-9]{1,20}$ — lowercase letters/digits, no hyphens
        name: "todo api", // display label only
        source: "src/index.ts", // entry file, relative to neon.ts
      },
    },
  },
});

The slug is the function's permanent identity (it appears in the invocation URL and CLI commands) and can't be changed after the first deploy. Use name for a human-readable label.

A minimal function — a Hono app that queries the branch's Postgres via the injected DATABASE_URL:

// src/index.ts
import { Hono } from "hono";
import { drizzle } from "drizzle-orm/node-postgres";
import { Pool } from "pg";
import { parseEnv } from "@neon/env";
import { attachDatabasePool } from "@neon/functions";
import config from "../neon";
import { todos } from "./db/schema";

const env = parseEnv(config);
const pool = new Pool({ connectionString: env.postgres.databaseUrl, max: 5 });
attachDatabasePool(pool);
const db = drizzle(pool);

const app = new Hono();
app.get("/", (c) => c.text("Neon + Hono + Drizzle"));
app.post("/todos", async (c) => {
  const { text } = await c.req.json<{ text: string }>();
  const [row] = await db.insert(todos).values({ text }).returning();
  return c.json(row, 201);
});
app.get("/todos", async (c) => c.json(await db.select().from(todos)));

export default app;