Master Slave
In plain terms
A model where one node controls or replicates to subordinate nodes.
Going deeper
In the master-slave (now often 'primary-replica') pattern, a primary handles writes and coordinates, while replicas copy data or do delegated work. It centralizes authority.
Under the hood
Common in database replication; the primary is a single point of failure unless failover exists. Terminology is shifting to primary/replica.
Examples
Database replication, primary-replica, distributed coordination, read scaling.
Think of it like...
Like a head chef directing line cooks who carry out the prepared instructions.