I'm not sure exactly what they were doing. It doesn't sound like anything novel. (Also doesn't sound like master/slave, which typically refers to a replication

I'm not sure exactly what they were doing. It doesn't sound like anything novel. (Also doesn't sound like master/slave, which typically refers to a replication setup) Sounds like they had some tables in one database and some tables in another. If they were using MySQL's built-in capabilities to do such a thing, and wanted to combine things at the database level there is already a specific term for that: federation. https://dev.mysql.com/doc/refman/5.6/en/federated-create-server.html https://dev.mysql.com/doc/refman/5.6/en/federated-create-ser... Or perhaps they took a more service-oriented approach, in which the databases don't talk directly to each other but instead expose their data via some application layer. In which case there's a term for that: a service-oriented architecture.