Quorum
In plain terms
The minimum number of nodes that must agree for an action to count.
Going deeper
Requiring a majority (quorum) to commit reads or writes ensures consistency and prevents split-brain when the network partitions. It's a building block of fault-tolerant systems.
Under the hood
With N replicas, requiring R+W > N for reads and writes guarantees overlap and consistency; tuning R and W trades latency vs. consistency.
Examples
3-of-5 node agreement, Cassandra QUORUM consistency, etcd majority writes.
Think of it like...
Like a board meeting needing more than half the members present before any decision is official.