The MongoDB Adapter uses the mongodb-erlang driver.
It takes two specific options, db_write_mode and db_read_mode which can be used to configure
write-mode and read-mode, as described in mongodb-erlang README file
By default, write-mode is set to safe and read-mode is set to master.
The adapter considers lists of integers and binaries as strings, so passing it values such as "hello" or <<"hello">> will result in a string object being stored in your database. If you actually need to store lists of integers, you will need to wrap them in a tagged tuple such as {integers, [1,2,3]} so that the adapter knows you really want to store a list of integers and not a string. A similar tuple will be returned when reading back from the database.
Raw queries can be made using execute/2 for things like MapReduce.
TODO: add raw queries examples.