Search in a Multi-Geo tenant
In a Multi-Geo tenant, each geo location has its own search index, as well as its own independent search center. When a user searches, the query is fanned out to all the indexes, and the returned results are merged.
For example, a user in one geo location can search for content stored in another geo location, or for content on a SharePoint site that’s restricted to a different geo location. If the user has access to this content, search shows the result.
To work programmatically with search in a Multi-Geo tenant, see Get custom search applications to show results from all or some geo locations.