Quorums

Majorities overlap#

In a five-node group, any majority contains three nodes. Two such majorities share at least one node, which can help prevent two independent groups from making incompatible decisions under a protocol's assumptions.

Some replicated-data models describe N replicas, W write acknowledgements, and R replicas consulted on reads. Under particular assumptions, R + W > N creates overlap. That relationship alone is not a universal strong-consistency recipe: timing, version selection, sloppy quorums, failures, and implementation semantics matter.