Connect Your App to Managed PostgreSQL with DATABASE_URL (Node.js, Python, Go)

Hard-coded database credentials are the classic way an app breaks between your laptop and production. The fix is old and simple: read one connection string, DATABASE_URL, from the environment, and let the platform fill it in.

This guide shows how that works with a managed PostgreSQL database on DockHosting, with copy-paste code for Node.js, Python and Go.

How it works#

1. Create a PostgreSQL database from the dashboard. It's ready in seconds.
2. Attach it to your project.
3. Its connection string is injected into every connected app as DATABASE_URL.

The database is reached over a private network through an internal hostname. Nothing is exposed to the internet by default, and your app and database sit in the same region (eu-central-1), so queries don't pay cross-region latency.

A DATABASE_URL looks like this:

postgresql://USER:PASSWORD@HOST:5432/DATABASE

Never commit it. Locally, put it in a .env file that's in .gitignore. In production, the platform sets it.

Node.js#

With node-postgres:

import pg from "pg";
 
export const pool = new pg.Pool({ connectionString: process.env.DATABASE_URL });
 
const { rows } = await pool.query("select id, email from users where id = $1", [userId]);

With Prisma, point the datasource at the variable:

datasource db {
  provider = "postgresql"
  url      = env("DATABASE_URL")
}

Drizzle, Knex, TypeORM and Sequelize take the same string. Always use parameterized queries ($1) rather than string concatenation to stay safe from SQL injection.

Python#

Django#

Install dj-database-url and read the variable in settings.py:

import dj_database_url
 
DATABASES = {"default": dj_database_url.config(conn_max_age=600)}

When manage.py is detected, migrate runs automatically before traffic switches to the new release, so your schema is always ahead of your code.

FastAPI / SQLAlchemy#

import os
from sqlalchemy import create_engine
 
url = os.environ["DATABASE_URL"].replace("postgresql://", "postgresql+psycopg://", 1)
engine = create_engine(url, pool_pre_ping=True)

The replace call selects the psycopg 3 driver. pool_pre_ping quietly replaces stale connections, which matters on the Free plan, where apps sleep when idle.

Go#

With pgx:

pool, err := pgxpool.New(ctx, os.Getenv("DATABASE_URL"))
if err != nil {
    log.Fatal(err)
}
defer pool.Close()
 
var now time.Time
err = pool.QueryRow(ctx, "select now()").Scan(&now)

Go apps compile to a single static binary on deploy and wake in under a second.

Running migrations#

• Django: migrate runs automatically on deploy.
• Rails: db:migrate runs automatically on deploy.
• Laravel: artisan migrate runs automatically on deploy.
• Node.js / Go: run your migration tool as part of your build or start command, for example "start": "prisma migrate deploy && node dist/server.js". You can override the build and start commands per project in the dashboard.

Querying from your terminal#

To check data quickly, dock db sql runs a SQL query against one of your managed databases from the CLI. You don't need to open a port or install a client. On Pro and Team you also get a database admin panel in the browser.

Limits by plan#

Free databases don't pause and don't expire. Read more on managed PostgreSQL hosting or compare plans.

Using other databases#

The same pattern works for every engine. MySQL and MariaDB use DATABASE_URL, MongoDB uses MONGODB_URI, Redis uses REDIS_URL and ClickHouse uses CLICKHOUSE_URL. Attach the database, then read the variable.

New to deploying? Start with deploying a Node.js app in one command.

Related: Moving a Render free Postgres before it's deleted · Free backend hosting with a database that doesn't expire