Raft Consensus Vocabulary

1. In Raft, the leader periodically sends empty AppendEntries messages to all followers to prevent them from starting an election. What are these messages called?

Keepalive probes Heartbeats Commit notifications

2. A Raft cluster has 5 nodes. How many nodes must acknowledge a log entry before the leader can mark it committed?

All 5 nodes Any 1 node At least 3 nodes (majority quorum)

3. The highest log entry index that the leader has safely replicated to a quorum of followers and applied to its state machine is called the:

Match index Commit index Last applied index

4. During a design review a colleague says: 'If a network partition splits our 5-node Raft cluster 3/2, the minority partition will reject writes.' Why is this correct?

Because the minority nodes automatically shut down Because the minority partition of 2 nodes cannot form a majority quorum, so no leader can be elected or commits accepted there — preventing split brain Because Raft uses a token-based system to block writes

5. Each Raft election increments a number that acts as a logical clock, distinguishing messages from the current leader from messages of stale or deposed leaders. What is this number called?

The epoch The term The round

Vocabulary Reference

Term	Meaning
heartbeat	Periodic empty AppendEntries message from leader to followers; resets their election timeout.
term	A monotonically increasing integer in Raft; each election begins a new term.
log entry	A command plus its term number stored in the replicated log; applied to state machines in order.
commit index	The highest log index known to be replicated to a quorum and therefore safe to apply.
majority quorum	More than half the nodes (n/2 + 1); required for elections and log commits in Raft.
split brain	A failure mode where two partitions each elect a leader, causing conflicting writes; Raft prevents this via quorum.

Vocabulary Reference

Exercise complete!