Learning series · 5 episodes · Staff / Principal
Who gets to decide?
Five lessons on Raft elections, current-term commitment, fencing, safe reads and changing voters.
Start series →Follow the decisions in order
- Part 1 of 5
Staff
The old leader is alive. Why won't the cluster accept its writes?Explain minority behavior, term-based elections, candidate freshness and the scope of reads under a network partition.
- Part 2 of 5
Staff
Three servers have the log entry. Why won't Raft commit it?Distinguish log replication from commitment of prior-term entries, and connect Raft terms, election restriction and current-term commitment.
- Part 3 of 5
Staff
The lease expired. Why can its previous owner still write?Distinguish lease expiration from the physical ability to write, and enforce non-regression with destination-side fencing.
- Part 4 of 5
Staff
The leader has applied every entry. Why might its read still be stale?Establish linearizable read authority using a quorum-confirmed read barrier and state-machine application, separate from local replay lag.
- Part 5 of 5
Principal
We added two voters. How could a routine change split the cluster?Prove overlapping authority across reconfiguration and plan learner promotion, joint consensus or sequential membership operations with failure recovery.