Raft split brain divergence

A 5-node distributed storage cluster (Raft-replicated key-value store) backing your billing ledger experiences a 90-second network partition that splits it 3|2. After the network heals, on-call sees: reads for some keys return different values depending on which node serves them; the cluster reports two nodes claiming to have been leader during the partition window; applied_index diverges between the two former groups; a small set of writes accepted during the partition is now in question. Latency is fine; the problem is correctness. Some customers were double-charged. How do you triage and resolve a suspected split-brain / replica divergence on durable data?