Hadoop Streaming Support for MongoDB
blog.mongodb.org/post/24610529795/hadoop-streaming-support-for-mongodb
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Using this adapter, it is possible to use MongoDB as a real-time datastore for your application while shifting large aggregation, batch processing, and ETL workloads to a platform better suited for the task.