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Replication Strategies — Overview

The simulator implements four replication strategies that cover the main design space of distributed databases. Each runs as an independent in-process cluster you can create, fault-inject, and inspect side by side.

Strategy comparison

Single-Leader Multi-Leader Leaderless Raft
Write target Leader only Any node Coordinator (any) Leader only
Write latency Low (async) / High (sync) Low Tunable (W) Medium
Read staleness Possible Possible Tunable (R) None (linearizable)
Conflict resolution None needed LWW / VC / CRDT Last-write-wins None needed
Fault tolerance Leader failover (manual) Partition-tolerant N − W + 1 failures Automatic re-election
Consistency model Sequential (async) / Linearizable (sync) Eventual Eventual / Strong (W+R>N) Linearizable
Real-world analogues PostgreSQL streaming, MySQL replication, Kafka CouchDB, Cassandra multi-DC, DynamoDB Global Tables Cassandra, DynamoDB, Riak etcd, CockroachDB, TiKV

CAP positioning

         Consistency
              │
         Raft ●
    Single-   │
    Leader ●  │
              │
──────────────┼──────────────
              │          Availability
              │
   Leaderless ●─────────────●  Multi-Leader
   (strong W+R>N)     (W+R≤N or
                       multi-leader)
  • Raft and sync single-leader sit at the CP corner: any partition that cuts off the leader stalls writes.
  • Async single-leader relaxes consistency slightly in exchange for lower write latency but still loses availability on leader failure.
  • Leaderless with W+R>N provides tunable strong consistency while surviving up to N − W + 1 simultaneous failures.
  • Multi-leader and leaderless with W+R≤N maximize availability at the cost of eventual consistency and the need for conflict resolution.

Deep dives

  • Single-Leader — leader/follower log replication, async/sync/semi-sync durability
  • Multi-Leader — vector clocks, conflict detection, LWW/VC/CRDT resolvers
  • Leaderless (Dynamo) — consistent hashing, sloppy quorums, hinted handoff, read repair
  • Raft — leader election, log matching, majority commit, snapshots