> ## Documentation Index
> Fetch the complete documentation index at: https://clickhouse.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Use Bun with ClickHouse Managed Postgres

> Connect a Bun application to ClickHouse Managed Postgres with the built-in Bun.sql client and verified TLS

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<BetaBadge link="https://clickhouse.com/cloud/postgres" galaxyTrack={true} galaxyEvent="docs.managed-postgres.guides-bun-beta" />

[Bun](https://bun.sh) is a JavaScript and TypeScript runtime with a built-in Postgres client, `Bun.sql`, so you don't need to install a driver.
In this guide, you connect Bun to ClickHouse Managed Postgres over verified TLS, create a table, run queries and a transaction, and serve the rows over HTTP with `Bun.serve`.

<h2 id="prerequisites">
  Prerequisites
</h2>

* [Bun](https://bun.sh/docs/installation) 1.4 or later. This guide was tested with Bun 1.4.2 and Postgres 18.
* A ClickHouse Cloud account.
* [`psql`](https://www.postgresql.org/download/), to create the database. You can also run the `CREATE DATABASE` statement in the [SQL console](/docs/integrations/connectors/sql-clients/sql-console).

<h2 id="create-service">
  Create a ClickHouse Managed Postgres service
</h2>

In the ClickHouse Cloud console, click **New service** and select **Postgres**. The instance is ready in a few minutes. See the [quickstart](/docs/products/managed-postgres/quickstart) for a walkthrough.

<h2 id="connection-details">
  Get your connection details
</h2>

Open your service and click **Connect** in the left sidebar. Keep **Directly** selected and turn on **Use SSL**. The URL now ends with `sslmode=verify-full&sslrootcert=...`. Click **Download CA certificate** to download the CA certificate for your instance.

This guide connects **directly** on port `5432`. A `Bun.serve` app is a long-running process, and `Bun.sql` keeps its own connection pool, so a server-side pooler isn't needed. If you run many short-lived Bun processes, see [Connect through PgBouncer](#pgbouncer).

<h2 id="setup">
  Set up the project
</h2>

Create a project:

```bash theme={null}
mkdir bun-postgres && cd bun-postgres
bun init -y
```

<Tip>
  **Adding to an existing app?**

  Skip `mkdir` and `bun init -y`, since `Bun.sql` is built into Bun and there's nothing to install. In your project root, continue with [Configure the connection](#configure), and also put `NODE_EXTRA_CA_CERTS=./ca-certificate.pem` in front of your app's own start script so it can verify the server.
</Tip>

<h2 id="configure">
  Configure the connection
</h2>

Move the CA certificate you downloaded into the project and rename it to `ca-certificate.pem`:

```bash theme={null}
mv ~/Downloads/<service-name>-ca-certificate.pem ca-certificate.pem
```

Create a database for the app. Replace `<PASSWORD>` and the host with the values from the **Connect** modal:

```bash theme={null}
psql "postgresql://postgres:<PASSWORD>@your-instance.pg.clickhouse.cloud:5432/postgres?sslmode=verify-full&sslrootcert=ca-certificate.pem" -c "CREATE DATABASE guide_bun;"
```

```text theme={null}
CREATE DATABASE
```

Add the connection URL for the `guide_bun` database to `.env`, creating the file if it doesn't exist. Bun loads `.env` automatically, and the `sql` export from `bun` reads `DATABASE_URL`:

```bash title=".env" theme={null}
DATABASE_URL=postgresql://postgres:<PASSWORD>@your-instance.pg.clickhouse.cloud:5432/guide_bun?sslmode=verify-full
```

URL-encode the password if it contains special characters. Keep `.env` out of version control.

Add these scripts to `package.json`, merging them into the `scripts` block if it already exists. They pass the CA certificate to Bun through `NODE_EXTRA_CA_CERTS`:

```json title="package.json" theme={null}
"scripts": {
  "setup": "NODE_EXTRA_CA_CERTS=./ca-certificate.pem bun run setup.ts",
  "queries": "NODE_EXTRA_CA_CERTS=./ca-certificate.pem bun run queries.ts",
  "serve": "NODE_EXTRA_CA_CERTS=./ca-certificate.pem bun run server.ts"
}
```

<Note>
  **How Bun verifies the server certificate**

  * `sslmode=verify-full` makes `Bun.sql` check both the certificate chain and the host name.
  * Don't copy the `sslrootcert` parameter from the console URL. `Bun.sql` doesn't read it. It forwards it to the server as a runtime setting, and the connection fails with `unrecognized configuration parameter "sslrootcert"`.
  * `NODE_EXTRA_CA_CERTS` must be set in the environment when Bun starts. Bun doesn't read it from `.env`, which is why it's in the scripts.
  * In Bun 1.4.2, passing the downloaded certificate through the `tls: { ca }` option of `SQL` fails with `certificate signature failure`. Use `NODE_EXTRA_CA_CERTS` instead.
</Note>

<h2 id="create-table">
  Create a table
</h2>

Create `setup.ts`. It prints the TLS state of the session and creates a `todos` table:

```ts title="setup.ts" theme={null}
import { sql } from "bun";

const [tls] = await sql`SELECT ssl, version FROM pg_stat_ssl WHERE pid = pg_backend_pid()`;
console.log("TLS:", tls);

await sql`
  CREATE TABLE IF NOT EXISTS todos (
    id         integer GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
    title      text NOT NULL,
    done       boolean NOT NULL DEFAULT false,
    created_at timestamptz NOT NULL DEFAULT now()
  )
`;
console.log("Table todos is ready");

await sql.close();
```

Run it:

```bash theme={null}
bun run setup
```

```text theme={null}
$ NODE_EXTRA_CA_CERTS=./ca-certificate.pem bun run setup.ts
TLS: {
  ssl: true,
  version: "TLSv1.3",
}
Table todos is ready
```

To confirm that the certificate is checked, run the file without the CA certificate. The connection is refused:

```bash theme={null}
bun run setup.ts
```

```text theme={null}
error: unable to verify the first certificate
 errno: 0,
  code: "UNABLE_TO_VERIFY_LEAF_SIGNATURE"
```

<h2 id="query">
  Query the database
</h2>

`Bun.sql` uses tagged templates. Every interpolated value is sent as a bind parameter, so it's safe to pass user input. Create `queries.ts`:

```ts title="queries.ts" theme={null}
import { sql } from "bun";

// Interpolated values are sent as bind parameters, never spliced into the SQL text
const title = "Download the CA certificate";
const [first] = await sql`INSERT INTO todos (title, done) VALUES (${title}, true) RETURNING *`;
console.log("Inserted:", first);

// Insert several rows at once with the sql(array) helper
const rows = [{ title: "Connect with Bun.sql" }, { title: "Serve rows with Bun.serve" }];
await sql`INSERT INTO todos ${sql(rows)}`;

// Both statements commit together, or neither does
await sql.begin(async (tx) => {
  const [todo] = await tx`INSERT INTO todos (title) VALUES ('Write a transaction') RETURNING id`;
  await tx`UPDATE todos SET done = true WHERE id = ${todo.id}`;
});

const open = await sql`SELECT id, title FROM todos WHERE done = ${false} ORDER BY id`;
console.log("Open todos:", open);

await sql.close();
```

`sql.begin` runs the callback in a transaction. It commits when the callback returns and rolls back if it throws.

Run it:

```bash theme={null}
bun run queries
```

```text theme={null}
$ NODE_EXTRA_CA_CERTS=./ca-certificate.pem bun run queries.ts
Inserted: {
  id: 1,
  title: "Download the CA certificate",
  done: true,
  created_at: 2026-09-30T16:51:23.040Z,
}
Open todos: [
  {
    id: 2,
    title: "Connect with Bun.sql",
  }, {
    id: 3,
    title: "Serve rows with Bun.serve",
  }, count: 2, command: "SELECT", lastInsertRowid: null,
  affectedRows: null
]
```

<h2 id="serve">
  Serve the rows over HTTP
</h2>

Create `server.ts` with a `/todos` endpoint that lists and creates rows:

```ts title="server.ts" theme={null}
import { sql } from "bun";

const server = Bun.serve({
  port: 3106,
  routes: {
    "/todos": {
      GET: async () => {
        const todos = await sql`SELECT id, title, done, created_at FROM todos ORDER BY id`;
        return Response.json(todos);
      },
      POST: async (req) => {
        const { title } = await req.json();
        const [todo] = await sql`INSERT INTO todos (title) VALUES (${title}) RETURNING *`;
        return Response.json(todo, { status: 201 });
      },
    },
  },
});

console.log(`Listening on ${server.url}`);
```

Start the server:

```bash theme={null}
bun run serve
```

```text theme={null}
$ NODE_EXTRA_CA_CERTS=./ca-certificate.pem bun run server.ts
Listening on http://localhost:3106/
```

In another terminal, add a row:

```bash theme={null}
curl -X POST http://localhost:3106/todos -H 'Content-Type: application/json' -d '{"title": "Take a screenshot"}'
```

```json theme={null}
{"id":5,"title":"Take a screenshot","done":false,"created_at":"2026-09-30T16:51:30.372Z"}
```

<h2 id="verify">
  Verify
</h2>

Open [http://localhost:3106/todos](http://localhost:3106/todos) in your browser to see all rows. The response looks like this, formatted for readability:

```json theme={null}
[
  {"id":1,"title":"Download the CA certificate","done":true,"created_at":"2026-09-30T16:51:23.040Z"},
  {"id":2,"title":"Connect with Bun.sql","done":false,"created_at":"2026-09-30T16:51:23.136Z"},
  {"id":3,"title":"Serve rows with Bun.serve","done":false,"created_at":"2026-09-30T16:51:23.136Z"},
  {"id":4,"title":"Write a transaction","done":true,"created_at":"2026-09-30T16:51:23.184Z"},
  {"id":5,"title":"Take a screenshot","done":false,"created_at":"2026-09-30T16:51:30.372Z"}
]
```

In the console, open **SQL console** and expand **guide\_bun**, then **public**, then **todos** to see the same rows:

| id | title | done | created\_at |
| - | - | - | - |
| 1 | Download the CA certificate | true | 2026-09-30 16:51:23.04083+00 |
| 2 | Connect with Bun.sql | false | 2026-09-30 16:51:23.136975+00 |
| 3 | Serve rows with Bun.serve | false | 2026-09-30 16:51:23.136975+00 |
| 4 | Write a transaction | true | 2026-09-30 16:51:23.184716+00 |
| 5 | Take a screenshot | false | 2026-09-30 16:51:30.372292+00 |

<h2 id="pgbouncer">
  Connect through PgBouncer
</h2>

If you run many short-lived Bun processes, connect through the bundled [PgBouncer](/docs/products/managed-postgres/connection#pgbouncer) instead. Select **via PgBouncer** in the **Connect** modal and change the port in `DATABASE_URL` to `6432`. The CA certificate and `sslmode=verify-full` stay the same.

PgBouncer runs in transaction pooling mode. `Bun.sql` uses named prepared statements by default, and in our tests they worked through PgBouncer with no errors. If you see `prepared statement does not exist` errors, create the client with `prepare: false`:

```ts theme={null}
import { SQL } from "bun";

const sql = new SQL(process.env.DATABASE_URL!, { prepare: false });
```

Pass `prepare` as an option, not in the URL. Like `sslrootcert`, a `prepare=false` URL parameter is forwarded to the server and rejected.

<h2 id="next-steps">
  Next steps
</h2>

* [Connection](/docs/products/managed-postgres/connection): connection strings, PgBouncer, and TLS
* [Settings](/docs/products/managed-postgres/settings): change Postgres and PgBouncer parameters
* [Read replicas](/docs/products/managed-postgres/read-replicas): scale reads
* [Bun SQL documentation](https://bun.sh/docs/runtime/sql): the full `Bun.sql` API