matchIndex
matchIndex is a term used in distributed consensus protocols, most commonly Raft, to describe, for each follower, the index of the highest log entry known to be stored on that follower. It is a piece of leader-maintained state that tracks replication progress and is distinct from the follower’s own log boundary. For a given follower, matchIndex is non-decreasing as the follower catches up.
In Raft, each follower is tracked by two values: nextIndex and matchIndex. The matchIndex for a follower
A primary use of matchIndex is determining when new entries can be considered committed. The leader can
Relation to persistence: matchIndex is typically volatile state kept by the leader and not persisted across