I'm sure that someone else can describe the actual history of Ndb development much better, but here's my limited and vague understanding.

• Ndb is developed in an environment (Ericsson AXE telecoms switch) where Ericsson's PLEX is the language of choice
  PLEX supports multiple state machines (known as blocks) sending messages (known as signals) between them with some system-level conventions for starting up, restart and message classes. Blocks maintain internal state and define signal handling routines for different signal types. Very little abstraction within a block beyond subroutines is supported. (I'd love to hear some more detail on PLEX and how it has evolved). This architecture maps directly to the AXE processor design (APZ) …

MySQL Cluster is the name given to one or more MySQL Server processes, connected to an Ndb Cluster database. From the point of view of the MySQL Server processes, the Ndb Cluster is a Storage Engine, implementing transactional storage of tables containing rows. From the point of view of the Ndb Cluster database, the MySQL Server processes are API nodes, performing DDL and DML transactions on tables stored in the cluster. Both exist independently – Ndb Cluster can be used without attached MySQL Server processes, but almost all users of Ndb Cluster connect at least one MySQL Server for DDL and administration.

Ndb stands for Network DataBase. This is a telecoms phrase where Network usually refers to a fixed or wireless telephone network, rather than the …