MMDB 2 is a complete rewrite of MMDB 1 (Medici). The code is now based on SCALA and the main goal of this version is scalability, both in terms of datasets as well as in extractors.
Another main difference between the two versions is the way extractors operator. Extractors now will connect to a message bus (rabbitmq by default) and wait for requests to extract information. The extractors will now be smaller and with this system more scalable.