Raft and Paxos

The two classic consensus algorithms. Raft elects a leader that replicates a log to followers and commits an entry once a majority has stored it; it is used by etcd, Consul and CockroachDB.

Where it shows up in real systems

  • Distributed SQL

    Each write is committed through a consensus protocol (Raft or Paxos), so it is never lost and every read is up to date, even across regions. The price is latency: a write must reach a majority of replicas, and across regions that means tens of milliseconds.

    In production: Google Cloud Spanner, CockroachDB, YugabyteDB, TiDB, Amazon Aurora DSQL

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