Amazon DocumentDB (with MongoDB compatibility) now supports new features for aggregations, arrays, and indexing
Amazon DocumentDB (with MongoDB compatibility) is a fast, scalable, highly available, and fully managed document database service that supports MongoDB workloads. Today, Amazon DocumentDB added support for new aggregation string operators ($concat, $substr, $substrBytes, $substrCP, $strcasecmp), an array aggregation operator ($size), an aggregation group accumulator operator ($push), and aggregation stages ($redact and $indexStats) that allow you to compose powerful aggregations over your documents. Additionally, Amazon DocumentDB now supports positional array operators ($[] and $[<identifier>]) for updating elements in an array and hint() for selecting an index.
To use the new features, you can create a new Amazon DocumentDB cluster with just a few clicks in the Amazon DocumentDB Management Console or you can upgrade your existing cluster.
For more information, see the AWS Database Blog: New Amazon DocumentDB feature for aggregations, array, and indexing