I have been doing a lot of work with Java. A lot of it in getting the     C++ and Java interfaces to align. So when I went looking for a database engine, I settled on H2 for the Java engine.

    Since you can run Raydo in an application, H2 can be run in an embedded mode, as well as HSQLDB and Derby. It can also be run as a client / server and a cluster.

The ‘plugin’ was added to the Java tree.
    So looking at the benchmarks, it seems that H2 is faster than HSQLDB & Derby in the embedded space, and comparable with Postgres and MySQL in the client/server space.

    Raydo uses the Slots and Signals pattern for communication. So just as an aside, I want to give a little background on this design pattern. We are using two models for signals and slots, and have not decided on which one to use. We may keep both.

    Signals and slots is a language construct (originally used by TrollTech in their QT project ) to implement the Observer pattern avoiding boilerplate code. A signal to slot connection is the same as the Design Pattern Observer

    The concept is that objects can send signals containing information which can be received by other objects using special functions known as slots. The signal/slot system can be used for asynchronous I/O including sockets, pipes, serial devices, etc.