An update from Microsoft Azure says that – As part of the transition from Azure DocumentDB to Azure Cosmos DB, the service and resource names are changing from “Azure DocumentDB” to “Azure Cosmos DB” on June 1, 2018.
How does that Impact?
When Microsoft introduced Cosmos DB, then have ensured that there was a smooth transition or migration of existing Document DB customers /tenants to Cosmos DB. This was achieved by without changing underlying service and resource names from “Document DB” to “Cosmos DB”.
So, if you were an existing customer of Document DB, you have noticed the only disappearance of Document DB name and old service showing simply Cosmos DB. You did not feel much difference apart from some additional configuration options as part of multi-modal data source configuration.
Your ARM deployment templates might need some changes in resource sizing, resource location, and some other configuration aspects.
There is no a pricing impact because of this change, but you will have to modify billing parameters that rely on the new names. Now with this deadline what Microsoft intends to have is to deprecate the use of Old DocumentDB naming and start migrating all customers/tenants to follow the new naming for the resource billing/sizing purposes.
To read more about the naming changes: https://azure.microsoft.com/en-us/updates/name-changes-cosmos-db/