View source for Quorum (distributed systems)

In [[Distributed systems|distributed systems]], a '''quorum''' is the minimum number of nodes whose agreement is required to perform an operation safely. The concept is the mathematical backbone of consensus protocols like [[Paxos]] and the [[Raft consensus algorithm|Raft algorithm]]: a value is only committed once a majority of nodes acknowledge it, ensuring that no two conflicting values can achieve majority simultaneously.

The simplest quorum is a '''majority''' of nodes, but more sophisticated schemes — weighted quorums, read/write quorums, and grid quorums — allow systems to trade latency, fault tolerance, and availability against each other. The [[CAP theorem]] constraint is visible here: a quorum system that tolerates more failures requires larger quorums, which increases the latency of every operation. The quorum is not merely a voting threshold; it is the system's safety boundary.

[[Category:Systems]]
[[Category:Computer Science]]