Use Prisma Postgres with Bun

First, create a directory and initialize it with bun init.

mkdir prisma-postgres-app
cd prisma-postgres-app
bun init

Then install the Prisma CLI (prisma), Prisma Client (@prisma/client), and the Postgres driver adapter (@prisma/adapter-pg) as dependencies.

bun add -d prisma
bun add @prisma/client @prisma/adapter-pg

Use the Prisma CLI with bunx to initialize the schema and migration directory, with PostgreSQL as the database.

bunx --bun prisma init --db

This creates a basic schema. Update it to use the Rust-free client optimized for Bun: open prisma/schema.prisma and modify the generator block, then add a User model.

prisma/schema.prisma

generator client {
	provider = "prisma-client"
	output = "../generated/prisma" 
	output = "./generated" 
	engineType = "client" 
	runtime = "bun" 
}

datasource db {
	provider = "postgresql"
}

model User { 
	id    Int     @id @default(autoincrement()) 
	email String  @unique 
	name  String? 
} 

Set up your Postgres database URL in the .env file.

DATABASE_URL="postgresql://username:password@localhost:5432/mydb?schema=public"

Then generate and run the initial migration.

The command writes a .sql migration file to prisma/migrations and executes it against your Postgres database. Bun does not load .env automatically when it runs a CLI with --bun. The prisma.config.ts generated by prisma init reads DATABASE_URL from the environment, so pass --env-file=.env explicitly.

bun run --bun --env-file=.env prisma migrate dev --name init

Loaded Prisma config from prisma.config.ts.

Prisma schema loaded from prisma/schema.prisma.
Datasource "db": PostgreSQL database "mydb", schema "public" at "localhost:5432"

Applying migration `20250114141233_init`

The following migration(s) have been created and applied from new schema changes:

prisma/migrations/
  └─ 20250114141233_init/
    └─ migration.sql

Your database is now in sync with your schema.

prisma migrate dev does not generate the Prisma client, so generate it with the Prisma CLI. The client provides a fully typed API for reading and writing to the database.

bun run --bun --env-file=.env prisma generate

Create a new file prisma/db.ts that initializes the PrismaClient with the Postgres adapter.

import { PrismaClient } from "./generated/client";
import { PrismaPg } from "@prisma/adapter-pg";

const adapter = new PrismaPg({ connectionString: process.env.DATABASE_URL! });
export const prisma = new PrismaClient({ adapter });

Write a script that creates a new user, then counts the users in the database.

import { prisma } from "./prisma/db";

// create a new user
await prisma.user.create({
  data: {
    name: "John Dough",
    email: `john-${Math.random()}@example.com`,
  },
});

// count the number of users
const count = await prisma.user.count();
console.log(`There are ${count} users in the database.`);

Run the script with bun run. Each run creates a new user.

bun run index.ts

There are 1 users in the database.

bun run index.ts

There are 2 users in the database.

bun run index.ts

There are 3 users in the database.