# domains

* `lunar-config.yml -> domains`
* Type: `object`
* Form:

  ```yaml
  domains:
    <domain-path>: <domain-object>
    <domain-path>: <domain-object>
    ...
  ```

Domains are used to group related components together. Domains are hierarchical and can contain other domains.

A domain's path is a string that uniquely identifies the domain. If a domain `bar` is within the domain `foo`, then the domain path is `foo.bar`.

Components under a domain receive the special tag `domain:<domain-name>` automatically. For example, components in the domain `foo.bar` will receive the tag `domain:foo.bar`. This tag can be used in [tag matching expressions](/configuration/lunar-config/on.md) to target components by domain.

Example domains defintion:

{% code title="lunar-config.yml" %}

```yaml
domains:
  saas-product:
    description: Acme's SaaS product
    owner: roberto@example.com
  saas-product.frontend:
    description: The frontend of Acme's SaaS product
    owner: jacqueline@example.com
  saas-product.frontend.ui-components:
    description: Common UI components for the frontend
    owner: jill@example.com
  saas-product.frontend.ui-common:
    description: Common UI code for the frontend
    owner: jane@example.com
  saas-product.frontend.ui-dashboard:
    description: The dashboard for the frontend
    owner: mary@example.com
  saas-product.frontend.ui-login:
    description: The login page for the frontend
    owner: jessica@example.com
  saas-product.backend:
    description: The backend of Acme's SaaS product
    owner: john@example.com
  saas-product.backend.auth:
    description: The authentication service for the backend
    owner: jesse@example.com
  saas-product.backend.rev-proxy:
    description: The reverse proxy for the backend
    owner: mike@example.com
  saas-product.backend.gateway:
    description: The gateway for the backend
    owner: larry@example.com
  widget-product:
    description: Acme's widget product
    owner: noah@example.com
  widget-product.frontend:
    description: The frontend of Acme's widget product
    owner: corey@example.com
  widget-product.data-processing:
    description: Data processing for Acme's widget product
    owner: ann@example.com
  common-infra:
    description: Common infrastructure
    owner: alice@example.com
    meta: # 🚧 Coming Soon
      "okta-team": "infra"
  common-infra.monitoring:
    description: Monitoring for common infrastructure
    owner: bob@example.com
  common-infra.logging:
    description: Logging for common infrastructure
    owner: todd@example.com
```

{% endcode %}

Domains are associated with components using the `domain` field in the [component definition](/configuration/lunar-config/components.md).

## Domain

* `lunar-config.yml -> domains.<domain-path>`
* Type: `object`
* Form:

  ```yaml
  description: <description>
  owner: <email>
  meta:                          # 🚧 Coming Soon
    <meta-key>: <meta-value>
    <meta-key>: <meta-value>
    ...
  ```

A domain is a group of related components. Domains are hierarchical and can contain other domains.

### `description`

* `lunar-config.yml -> domains.<domain-path>.description`
* Type: `string`
* Optional

A description of the domain.

### `owner`

* `lunar-config.yml -> domains.<domain-path>.owner`
* Type: `string`
* Optional

The email address of the owner of the domain.

### `meta` 🚧 Coming Soon

* `lunar-config.yml -> domains.<domain-path>.meta`
* Type: `object`
* Optional

A key-value store of arbitrary metadata for the domain. This metadata is not used by Lunar, but can be used by collectors and policies.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs-lunar.earthly.dev/configuration/lunar-config/domains.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.