Use this skill when working on Raft replication, consensus state, or log/application ordering.

Core safety rules:

• Only the leader accepts writes; followers replicate and apply in order.

• Log matching property must hold; conflicting entries are overwritten.

• Commit index advances only when entries are replicated to a quorum.

Implementation guidance:

• Identify the Raft module boundaries and avoid mixing consensus logic with storage or API layers.

• Keep persistence of log/state separate from in-memory state machines.

• Ensure snapshot installation and log truncation are consistent with the applied index.

• Membership changes must follow the project’s chosen approach (joint consensus or staged transitions).

• When adding new commands, ensure they are deterministic and idempotent when applied.

Testing focus:

• Leader failover and re-election.

• Log divergence and recovery.

• Snapshot restore and state replay.

Pitfalls:

• Applying out-of-order entries.

• Committing entries without quorum.

• Mixing wall-clock time with term/index logic.