Azure Cosmos DB supports aggregate functions
We have expanded the SQL grammar in Azure Cosmos DB to support aggregate functions.
Whether you’re building a mobile game that needs to calculate statistics based on completed games, designing an IoT platform that triggers actions based on the number of occurrences of a certain event, or building a simple website or paginated API, you need to perform aggregate queries against your operational database. With Azure Cosmos DB, you can now perform aggregate queries against data of any scale with low latency and predictable performance.
To learn more, see the Planet scale aggregates with Azure Cosmos DB blog post.