Galera wsrep provider is a dlopenable generic replication library which implements the wsrep provider API. It provides very efficient synchronous replication, and multi-master and "parallel applying" capabilities for opaque data buffers. Its primary focus is data consistency. A transaction is either committed on every node, or not at all. It works anywhere TCP works, including on WAN, and can utilize UDP multicast where available. It is used by the MySQL-wsrep patch project to create true multi-master MySQL/InnoDB clusters.
Crack is a programming language that aims to provide the ease of development of a scripting language with the performance of a compiled language. The "crack" program is a "script executor" that compiles source to machine code on the fly, though it will cache the code to intermediate formats as appropriate. The crack language itself derives concepts from C++, Java, and Python, incorporating object-oriented programming, operator overloading, and strong typing.
NNDB is a C++ library that provides in-memory data storage and retrieval using syntax that is intended to feel natural for C++/STL, but which also might feel slightly like SQL if you squint and pound the top of your head with a seminal programming textbook. Columns types are fixed at compile-time and checked by the compiler.