The Azure Data Factory/Azure Cosmos DB connector is now integrated with the Azure Cosmos DB bulk executor library to provide the best performance.
Data Factory now supports writing to Azure Cosmos DB by using UPSERT in addition to INSERT.
You can find the configuration in the Data Factory UI both for pipeline activity authoring and for the Copy Data tool wizard. For the Azure Cosmos DB sink, you can choose upsert or insert.
For more information, see the documentation. For hybrid copy by using the Self-hosted Integration Runtime, this feature is supported beginning in version 3.9 (July release).