xDB index
Overview of Sitecore xDB index supported infrastructure, references, and privacy and security.
The xDB index contains contact and interaction data, and is updated by the xConnect Search Indexer service.
You can host the xDB index on:
Solr
Azure Search
Refer to the Sitecore compatibility table for compatible versions.
The xDB index has its place in the Sitecore reference structure. It can be referenced by other roles, and it can also reference other roles.

Referenced by
The xDB index is referenced by the following roles:
References
The xDB index does not reference other roles.
The xDB index is used in the following data flows and processes:
The xDB index handles personal data in the following ways:
Contains personal data if the xConnect Search Indexer has been configured to index facets marked
[PIISensitive]
.