If you delete a custom integration, any custom data that integration previously wrote onto entities is not automatically removed. The old key/value will remain on each entity until you delete it manually.
To clean up the custom data key (for example, `cortex-data-dev`):
- Identify all entities that have the custom data key
- Use the List Entities API with the `query` parameter to search for the custom data key/value (similar to catalog search).
- Delete the custom data per entity
There is no bulk API to delete a custom data key across all entities, so the supported approach is to run this as a one-off script that pages through matching entities and issues the delete call for each entity.
For more information, see [Custom data advanced](https://docs.cortex.io/api/readme/custom-data/custom-data-advanced).