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

# Configuration

> Learn how to configure Esix for your MongoDB database, including connection settings, environment variables, and advanced configuration options.

Esix makes it easy to configure your database connection for different
environments (local, test, and production) using environment variables. This
approach helps keep your configuration flexible and secure.

## Database Connection Options

Here are the environment variables you can use to configure your database
connection:

### `DB_ADAPTER`

The adapter handles the MongoDB connection. You can choose between:

* `default` - Uses the
  [official MongoDB package](https://www.npmjs.com/package/mongodb) for
  production
* `mock` - Uses [mongo-mock](https://github.com/williamkapke/mongo-mock) which
  is perfect for testing

**Default:** `default`

### `DB_URL`

The connection URL for your MongoDB database.

**Default:** `mongodb://127.0.0.1:27017/`

**Example:**

```bash theme={null}
DB_URL=mongodb://localhost:27017/
# or for MongoDB Atlas
DB_URL=mongodb+srv://username:password@cluster.mongodb.net/
```

### `DB_MAX_POOL_SIZE`

The maximum number of connections in the connection pool. This helps manage
database performance under load.

**Default:** `10`

### `DB_DATABASE`

The name of the database to connect to.

**Default:** (empty string)

**Example:**

```bash theme={null}
DB_DATABASE=myapp_production
```

### `DB_LOG_QUERIES`

Enables the built-in query logger. When set to `1` or `true`, Esix logs every
MongoDB operation to the console using `console.debug`, including the
collection, operation, arguments, and duration.

**Default:** (disabled)

**Example:**

```bash theme={null}
DB_LOG_QUERIES=true
```

## Setting Up Environment Variables

For local development, we recommend using the
[dotenv package](https://www.npmjs.com/package/dotenv) to manage your
environment variables:

```bash theme={null}
npm install dotenv
```

Create a `.env` file in your project root:

```bash theme={null}
DB_URL=mongodb://localhost:27017/
DB_DATABASE=myapp_development
DB_MAX_POOL_SIZE=5
```

Then load it in your application:

```ts theme={null}
import 'dotenv/config'
// Your Esix code here
```

> **⚠️ Security Note:** Never commit secrets or production credentials to
> version control. Add `.env` to your `.gitignore` file!

## Query Logging

Query logging is opt-in and has zero overhead when disabled. The quickest way to
turn it on is the `DB_LOG_QUERIES` environment variable, which logs every
MongoDB operation with `console.debug`:

```
esix blog-posts.findOne([{"_id":"5f3568f2a0cdd1c9ba411c43"}]) took 0.8ms
```

For full control over where the entries go, register a custom logger with
`setQueryLogger`. The custom logger takes precedence over the built-in console
logger:

```ts theme={null}
import { setQueryLogger } from 'esix'

setQueryLogger((entry) => {
  console.log(
    `${entry.collectionName}.${entry.operation} took ${entry.durationMs.toFixed(1)}ms`
  )
})
```

Each entry contains:

* `args` - the arguments passed to the driver method
* `collectionName` - the collection the operation ran against
* `durationMs` - how long the operation took, in milliseconds
* `error` - the error the operation rejected with, if any
* `operation` - the driver method that was invoked, e.g. `find` or `updateOne`

Pass `null` to clear the custom logger again:

```ts theme={null}
setQueryLogger(null)
```

For Effect-managed connections and Config integration, see
[Effect configuration](/docs/effect#configuration-and-connection-lifetime).