Kyoto Tycoon is a lightweight database server with auto expiration mechanism,
which is useful to handle cache data and persistent data of various
applications. Kyoto Tycoon is also a package of network interface to the DBM
called Kyoto Cabinet. Though the DBM has high performance and high concurrency,
you might bother in case that multiple processes share the same database, or
remote processes access the database. Thus, Kyoto Tycoon is provided for
concurrent and remote connections to Kyoto Cabinet. Kyoto Tycoon is composed of
the server process managing multiple databases and its access library for client
applications.

The network protocol between the server and clients is HTTP so that you can
write client applications and client libraries in almost all popular languages.
Both of RESTful-style interface by the GET, HEAD, PUT, DELETE methods and
RPC-style inteface by the POST method are supported. The server can handle more
than 10 thousand connections at the same time because it uses modern I/O event
notification facilities such as "epoll" and "kqueue" of underlying systems. The
server supports high availability mechanisms, which are hot backup, update
logging, and asynchronous replication. The server can embed Lua, a lightweight
script language so that you can define arbitrary operations of the database.

WWW: http://fallabs.com/kyototycoon/