Using Azure Event Hubs Capture to stream data into Cosmos DB will not incur any extra charges. However, it is important to note that in the Standard tier of Azure Event Hubs, the traffic is controlled by throughput units and Event Hubs Capture charges $73 per month per throughput unit. In the Premium tier, traffic is controlled by processing units and the achievable throughput depends on various factors such as payload size, partition count, egress request rate, and usage of Event Hubs Capture. It is recommended to use the Premium tier for high-end streaming scenarios that require elastic and superior performance with predictable latency.
Additionally, Event Hubs Capture copies data directly from the internal Event Hubs storage, bypassing throughput unit or processing unit egress quotas and saving your egress for other processing readers, such as Stream Analytics or Spark. Once configured, Event Hubs Capture runs automatically when you send your first event and continues running. The destination storage account (Azure Storage or Azure Data Lake Storage) must be in the same subscription as the event hub and supports any storage account with support for block blobs.
References:
- Capture events through Azure Event Hubs in Azure Blob Storage or Azure Data Lake Storage: https://video2.skills-academy.com/en-us/azure/event-hubs/event-hubs-capture-overview#how-event-hubs-capture-works
- Overview of Event Hubs Premium: https://video2.skills-academy.com/en-us/azure/event-hubs/event-hubs-premium-overview