LMDB is a read-optimized Berkeley DB replacement developed by Symas for the OpenLDAP project. LMDB has impressive performance characteristics and a friendly BSD-style OpenLDAP license. See <http://symas.com/mdb/>.
This library has Haskell bindings to the LMDB library. You must install the lmdb development files before installing this library, e.g.
sudo apt-get install liblmdb-devworks for Ubuntu 14.04.
For now, only a low level interface is provided, and the author is moving on to use LMDB rather than further develop its bindings. If a higher level API is desired, please consider contributing, or develop a separate package.