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.
hamsterdb's first submission was in September 2006. It's a DBM-like library written in ANSI-C concentrating on high performance. It can run as in-memory database, use memory-mapped I/O, supports database cursors, variable length keys and records and can handle multiple databases per file.