This document provides an overview of using MongoDB for big data applications. It describes what MongoDB is, including that it is a open-source, document-oriented NoSQL database. It then covers some key MongoDB concepts and features like replica sets for high availability, sharding for horizontal scaling, and using MapReduce and Apache Spark with MongoDB. The document concludes that MongoDB is a fast, flexible, and scalable database solution for big data, though deploying sharded clusters requires planning.