MongoDB is a popular open source and document oriented database system. It belongs to a family of databases called NoSQL, which is different from the traditional table based SQL databases. It makes use of collections, each having multiple documents, and allows the user to store data in a non relational format. Data is stored in flexible, JSON-like documents where fields can vary from document to document. That's the reason for calling it schemaless database.
Based on the analysis of 190 studies, the average silent reading rate for adults in English is 238 words per minute for non-fiction and 260 words per minute for fiction. The difference can be predicted by taking into account the length of the words, with longer words in non-fiction than in fiction.