hamsterdb Embedded Storage is an embedded database engine for C/C++, including wrappers for Java, .NET, and Erlang. It supports in-memory databases, very fast database cursors, "record number" databases, ACID transactions, and duplicate keys. hamsterdb is very fast and highly configurable. It compiles and runs on Unix platforms, Linux, Microsoft Windows, and embedded platforms.
epers stands for "Erlang persistence". As the name suggests, it tries to make it easy to use databases in Erlang programs, to make the language a little more agile, and (humbly) offer a nice adapter for several databases, hiding their implementation details (and the API of the library/framework/driver used to communicate with them). To achieve this, it aims to offer a somewhat consistent API to define and work with your model, while at the same not coupling your code too tightly to it.