Amazon DocumentDB (with MongoDB compatibility) adds support for $mergeObjects and $reduce

Amazon DocumentDB is a scalable, highly durable, and fully managed database service for operating mission-critical MongoDB workloads.

Amazon DocumentDB continues to increase compatibility with MongoDB and today added support for the following MongoDB APIs and indexing improvements in DocumentDB 3.6 and 4.0:

• $mergeObjects: Aggregation pipeline operator that combines multiple documents into a single document
• $reduce: Aggregation operator that applies an expression to each element in an array and combines them into a single value

These capabilities are supported in all regions where Amazon DocumentDB is available. All supported MongoDB APIs and aggregation pipeline capabilities for Amazon DocumentDB can be found here. If you are new to Amazon DocumentDB, the getting started guide will show you how to quickly provision an Amazon DocumentDB cluster and explore the flexibility of the document model. Have questions or feature requests? Email us at: documentdb-feature-request@amazon.com.