FB/Java is a plugin for FB external engines feature, to be presented in
v3.0, that allows execution of Java code at the server side. The plugin
allows classes/resources in the file system or stored in the database.
File system classes/resources are global and the code run with all
permissions. Database classes/resources are per-database and code runs
accordingly with per-engine configured security policy.
Also it seems that is quite fast from Adriano’s tweets