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

# Records

> Manage records in Cognite Data Fusion (CDF).

Records are immutable or mutable data objects, depending on the stream template, that are stored in a stream. You create records by ingesting data into a stream.

For a comprehensive guide on records, including detailed behavior, uniqueness constraints, and how they relate to streams, see [About records and streams](/cdf/dm/records/concepts/records_and_streams).

Records have a similar shape to instances in the Data Modeling service, and their schema is defined by the [containers](/cdf/dm/dm_concepts/dm_containers_views_datamodels#containers) referenced as sources. Each record also links to the [space](/cdf/dm/dm_concepts/dm_spaces_instances#space) it belongs to, enabling space-based access control.

<Note>
  Every `record` has a required top-level `externalId` property, which you can use in some queries to retrieve or aggregate records.

  * **Mutable records**: The `externalId` and `space` properties uniquely identify records for write operations (create/upsert/delete).
  * **Immutable records**: The uniqueness of the `space` + `externalId` pair is not enforced, allowing multiple records with the same identifier to exist.
</Note>

## Rate and concurrency limits

For Records rate and concurrency limits, including mutable vs immutable stream budgets, see [API rate limits](/api-reference/concepts/20230101/rate-limits#records).