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Type-Safe Database Access at the Edge with Next 13 & PlanetScale

Read and render typesafe data at the Edge in Next 13


It's been a crazy week in the world of web development! Next 13's release has brought in an exciting new paradigm for developing websites using React Server components (RSCs), Next layouts and more.

What I'm most excited about are the new data fetching patterns introduced that allow you to fetch data directly in React Server Components, even going as far as connecting directly to your database.

After going semi-viral Tweeting:

I brainstormed some ways I could extend this further.

There are two problems with the code above. One is that the data I am fetching using PlanetScale's edge compatible serverless driver is not typesafe (thanks for pointing this out, Theo!), and also, I am not detecting the requests location in order to route it to a geographically closer database!

While edge computing is super exciting (no cold starts, extremely low latency!), there are still some considerations you need to make when requesting data from an external data source. For example, if our Database is located in Portland, Oregon but we have users requesting our edge functions or edge rendered pages that fetch data in Singapore, the query needs to travel to Portland to our database, back to the Singapore edge function. If you cannot bring the data source as close to an edge node as possible, a lot of the latency benefits are nullified. If only we could somehow detect where the user is pinging our app from, and direct them to a read-only replica of our database that is as close as possible geographically to them. And on the dev side, do so in a type safe manner.

Thanks to the amazing work done by Vercel, PlanetScale and the React team, this is entirely possible all without leaving your Next 13 code. Enter PlanetScale portals, Kysely, and Next 13's edge runtime.

As always, if you'd prefer to just jump into the code visit the repository here which mirrors what we will be implementing in this article.


In order to make use of PlanetScale Portals (global read replicas), you will need to enroll in a PlanetScale scalar plan. Keep in mind, the pattern I will lay out in this article is, in 99% of cases, an unnecessary optimization. You can get away fine with routing the user to a single database region. However, we want to over engineer the shit out of this and show what kind of speed is possible! So it will cost a bit.

Let's go.



I'll skip over a decent amount of the PlanetScale setup since I covered this in another article, but make sure to enable the Serverless driver setting in your PlanetScale account. We'll be using Prisma purely for generating types from our schema for usage in Kysely, as well as pushing updates to PlanetScale, so make sure to enable those features as well.

Enable serverless setting in PlanetScale

Once you've upgraded your plan to Scalar, go ahead and create as many read replica regions as you want! Make sure to generate the connection details for the region and save for later. In this tutorial we'll be creating replicas in all the offered regions.

Add a region in PlanetScale

NextJs & Prisma

Let's get started with Next! Go ahead and initialize a new Next 13 application with the experimental app directory by running

npx create-next-app@latest --experimental-app

We'll need a few dependencies for this demo, one of which is the Kysely PlanetScale Dialect which will give us a type safe query builder around our database schema as well as @planetscale/database.

Make sure to also initialize Prisma. We'll be setting up a PlanetScale compatible schema with a simple Model Game to query at the edge.

generator client {
  provider        = "prisma-client-js"
  previewFeatures = ["referentialIntegrity"]

datasource db {
  provider     = "mysql"
  url          = env("DATABASE_URL")
  relationMode = "prisma"

model Game {
  id        String   @id @default(cuid())
  createdAt DateTime @default(now())
  updatedAt DateTime @updatedAt
  score     Float
  completed Boolean  @default(false)

Connect to your primary branch, and push your schema updates with

npx prisma db push

Taking those connection details for each of your PlanetScale portal regions earlier, make sure to include the environment variables in your project in your .env.local file. I've used the following naming structure for this demo:


Now that we've got our config setup out of the way. Let's write some code!


Create a new file in lib/db.ts and start by importing Kysely, Kysely PlanetScale Dialect, and our Game table type from our Prisma client. Kysely PlanetScale Dialect will provide us with a type safe query builder around our serverless PlanetScale database. Let's also set up our types for our DB Read replicas, the Geolocations of our database regions, and our DB Kysely interface. We'll be storing the longitude and latitude of each of our database cities as well for comparison later.

import { Game } from '@prisma/client/edge';
import { Kysely } from 'kysely';
import { PlanetScaleDialect } from 'kysely-planetscale';

interface DbGeoLocation {
    latitude: number;
    longitude: number;
interface DB {
    Game: Game;
interface ConfigWithGeoLocation {
    dbConnection: Kysely<DB>;
    geoLocation: DbGeoLocation;

const connect = (username: string, password: string): Kysely<DB> => {
    return new Kysely<DB>({
        dialect: new PlanetScaleDialect({
            host: 'aws.connect.psdb.cloud',

export const usWest2 = connect(
    process.env.US_WEST_2_USERNAME as string,
    process.env.US_WEST_2_PASSWORD as string,

export const usEast1 = connect(
    process.env.US_EAST_1_USERNAME as string,
    process.env.US_EAST_1_PASSWORD as string,

export const euCentral1 = connect(
    process.env.EU_CENTRAL_1_USERNAME as string,
    process.env.EU_CENTRAL_1_PASSWORD as string,

const euWest1 = connect(
    process.env.EU_WEST_1_USERNAME as string,
    process.env.EU_WEST_1_PASSWORD as string,

const euWest2 = connect(
    process.env.EU_WEST_2_USERNAME as string,
    process.env.EU_WEST_2_PASSWORD as string,

const apNorthEast1 = connect(
    process.env.AP_NORTHEAST_1_USERNAME as string,
    process.env.AP_NORTHEAST_1_PASSWORD as string,

const apSouthEast1 = connect(
    process.env.AP_SOUTHEAST_1_USERNAME as string,
    process.env.AP_SOUTHEAST_1_PASSWORD as string,

const apSouthEast2 = connect(
    process.env.AP_SOUTHEAST_2_USERNAME as string,
    process.env.AP_SOUTHEAST_2_PASSWORD as string,

const apSouth1 = connect(
    process.env.AP_SOUTH_1_USERNAME as string,
    process.env.AP_SOUTH_1_PASSWORD as string,

const saEast1 = connect(
    process.env.SA_EAST_1_USERNAME as string,
    process.env.SA_EAST_1_PASSWORD as string,

const dbConnectionsWithGeoLocation: ConfigWithGeoLocation[] = [
        // Frankfurt
        dbConnection: euCentral1,
        geoLocation: {
            latitude: 50.110924,
            longitude: 8.682127,
        // Dublin
        dbConnection: euWest1,
        geoLocation: {
            latitude: 53.35014,
            longitude: -6.266155,
        // London
        dbConnection: euWest2,
        geoLocation: {
            latitude: 51.507359,
            longitude: -0.136439,
        // Portland, Oregon
        dbConnection: usWest2,
        geoLocation: {
            latitude: 45.523064,
            longitude: -122.676483,
        // Northern Virginia
        dbConnection: usEast1,
        geoLocation: {
            latitude: 37.926868,
            longitude: -78.024902,
        // Tokyo
        dbConnection: apNorthEast1,
        geoLocation: {
            latitude: 35.6762,
            longitude: 139.6503,
        // Singapore
        dbConnection: apSouthEast1,
        geoLocation: {
            longitude: 103.851959,
            latitude: 1.29027,
        // Sydney
        dbConnection: apSouthEast2,
        geoLocation: {
            longitude: 151.2099,
            latitude: -33.865143,
        // Mumbai
        dbConnection: apSouth1,
        geoLocation: {
            longitude: 72.877426,
            latitude: 19.07609,
        // Sao Paulo
        dbConnection: saEast1,
        geoLocation: {
            longitude: -46.62529,
            latitude: -23.533773,


Now comes the fun part. How do we leverage the longitudes and latitudes provided by next/headers and as well as the geolocation helper from the @vercel/edge package to find the closest read-only database replica to our request?

After doing some digging, we need to calculate a distance commonly referred to as "Crow flies distance", or the shortest straight line distance from point A to point B. We'll be looping through each of our database configs, calculating the crow flies distance between the request longitude and latitude with the database geo-location, and tracking what our closest config is.

The beauty of the edge runtime is that we still have access to Math V8 primitives (among other APIs), so we can use a simple formula to calculate the distance between our request location, and the read-replica database location.

Create a new file in helpers called geoLocation

// helpers/geoLocation
// Calculate the crows distance between two geo locations
export function calcCrow(lat1: number, lon1: number, lat2: number, lon2: number): number {
    const R = 6371; // km
    const dLat = toRad(lat2 - lat1);
    const dLon = toRad(lon2 - lon1);
    const lat1Rad = toRad(lat1);
    const lat2Rad = toRad(lat2);

    const a =
        Math.sin(dLat / 2) * Math.sin(dLat / 2) +
        Math.sin(dLon / 2) * Math.sin(dLon / 2) * Math.cos(lat1Rad) * Math.cos(lat2Rad);
    const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    const d = R * c;
    return d;

// Value to radians
function toRad(value: number): number {
    return (value * Math.PI) / 180;

Hop back over to our lib/db.ts file, and let's import calcCrow

import { calcCrow } from 'helpers/geoLocation';

And create a function that performs our calculation and looping. We'll default to usWest2, and initialize our closest distance to the MAX_SAFE_INTEGER

// lib/db.ts
const dbConnectionsWithGeoLocation: ConfigWithGeoLocation[] = [
// ...
export const closestDbConnection = (
    longitude: string | number,
    latitude: string | number,
): Kysely<DB> => {
    let closestConnection = usWest2;
    let closestDistance = Number.MAX_SAFE_INTEGER;

    dbConnectionsWithGeoLocation.forEach((config) => {
        const distanceBetweenLocationAndConfig = calcCrow(

        if (distanceBetweenLocationAndConfig < closestDistance) {
            closestConnection = config.dbConnection;
            closestDistance = distanceBetweenLocationAndConfig;
    return closestConnection;

Edge Functions

Phew. Now that all the grunt work is out of the way, it's time to put this all into action. First, let's create a default edge function that will be using our default usWest2 config so we can benchmark our performance globally compared to the function which will be swapping our DB connection at the edge.

Create pages/api/default.ts

import { usWest2 } from 'lib/db';

export const config = {
    runtime: 'experimental-edge',

export default async function handler() {
    const games = await usWest2.selectFrom('Game').selectAll().execute();

    return new Response(JSON.stringify({ games }), {
        status: 200,
        headers: {
            'content-type': 'application/json;charset=UTF-8',
            'access-control-allow-origin': '*',

Once you deploy this to Vercel (don't forget to set your Environment variables!), we'll be using KeyCDN's tool to test our endpoint. If you paste in the deployed Vercel URL with /api/default you can test the endpoint globally. Here's about the perf I am getting without swapping our connection at the edge.

Default edge perf

Not bad! But we can go faster.

Create a new endpoint in pages/api/edge-swap-db.ts that imports our closestDbConnection helper, using the geoLocation helper from @vercel/edge to extract our requests longitude and latitude, passing it in and finding our closest connection.

import { geolocation } from '@vercel/edge';
import { closestDbConnection } from 'lib/db';

export const config = {
    runtime: 'experimental-edge',

export default async function handler(req: Request) {
    const { longitude, latitude } = geolocation(req);

    const games = await closestDbConnection(longitude ?? '0', latitude ?? '0')

    return new Response(JSON.stringify({ games }), {
        status: 200,
        headers: {
            'content-type': 'application/json;charset=UTF-8',
            'access-control-allow-origin': '*',

Trigger a redeploy, and test this new endpoint on KeyCDN

Swapped edge perf



But wait, there's more!!

Server Components

Our examples above were using Edge functions, but we want to use Next 13! Thankfully, the headers object from the next/headers import can provide us our longitude and latitude in React Server Components, so we can use this same function.

First sure your next.config has these experimental options enabled.

/** @type {import('next').NextConfig} */
const nextConfig = {
    experimental: {
        appDir: true,
        runtime: 'experimental-edge',

module.exports = nextConfig;

In our shiny new app folder, create a page.tsx file alongside a simple root layout, and let's do some data fetching with our edge db config!

// app/page.tsx
import { headers } from 'next/headers';
import { closestDbConnection } from 'lib/db';

async function getData() {
    const longitude = headers().get('x-vercel-ip-longitude') ?? '0';
    const latitude = headers().get('x-vercel-ip-latitude') ?? '0';

    const games = await closestDbConnection(longitude, latitude)

    return games;

export default async function Page() {
    const games = await getData();
    return (
            {games.map((game) => (
                <div key={game.id}>{JSON.stringify(game)}</div>

You'll notice in your code editor, we get type safety and auto completion in our templates for the previous work we did with Kysely! Pretty awesome.

Keep in mind, since we are using our DB client directly and not fetch, the code above is similar to getStaticProps in Next < 13. If you want to revalidate the data on an interval, you could use a Segment Cache Configuration like

export const revalidate = 3600; // revalidate every hour

Wrap up

Well there you have it. We have utilized PlanetScale Portals, PlanetScale's Serverless Driver, Kysely, and Next 13 to detect where a request is coming from, and swap our DB connection at the edge to bring our data source as close as possible to the edge node, in a type safe manner!

If you want to check out the code, visit the repository here.

Thanks for reading!

Last updated

November 1, 2022