Consensus

aid: consensus
url: https://raw.githubusercontent.com/api-evangelist/consensus/refs/heads/main/apis.yml
name: Consensus
kind: topic
description: Consensus is the distributed systems problem of getting a set of unreliable processes to agree on a value or
  sequence of values. Consensus algorithms power state-machine replication for databases, key-value stores, configuration
  systems, and blockchains. The consensus topic spans classical crash-fault tolerant algorithms (Paxos, Raft, Multi-Paxos,
  Zab, Viewstamped Replication) and Byzantine fault tolerant algorithms (PBFT, Tendermint, HotStuff, Casper FFG/CBC), and
  the impossibility result FLP that bounds what is possible in fully asynchronous models.
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
tags:
- Algorithms
- BFT
- Blockchain
- Consensus
- Crash Fault Tolerance
- Distributed Systems
- Replication
- State Machine
created: '2025-01-01'
modified: '2026-04-28'
specificationVersion: '0.19'
apis:
- aid: consensus:paxos
  name: Paxos
  description: Paxos is the classical crash-fault-tolerant consensus algorithm introduced by Leslie Lamport in 1989. Paxos
    and its derivatives (Multi-Paxos, Cheap Paxos, Vertical Paxos, EPaxos, Flexible Paxos) are foundational to distributed
    systems theory and are used in Google Chubby, Spanner, Megastore, and others.
  humanURL: https://lamport.azurewebsites.net/pubs/paxos-simple.pdf
  baseURL: https://lamport.azurewebsites.net
  tags:
  - Lamport
  - Paxos
  - Replication
  properties:
  - type: Specification
    url: https://lamport.azurewebsites.net/pubs/paxos-simple.pdf
  - type: Reference
    url: https://www.cs.utexas.edu/users/lorenzo/corsi/cs380d/papers/paper2-1.pdf
  - type: Reference
    url: https://en.wikipedia.org/wiki/Paxos_(computer_science)
  x-features:
  - Tolerates up to f crash failures with 2f+1 acceptors
  - Phases prepare, promise, accept, accepted
  - Multi-Paxos pipelines decisions for log replication
  - Underlies Google Chubby and Spanner
  x-useCases:
  - Replicated state machines
  - Distributed configuration services (Chubby, ZooKeeper-like)
  - Globally consistent databases
- aid: consensus:raft
  name: Raft
  description: Raft is a consensus algorithm designed for understandability, published by Ongaro and Ousterhout in 2014. Raft
    separates leader election, log replication, and safety into distinct concepts and is implemented widely in etcd, Consul,
    CockroachDB, TiKV, MongoDB, and many other production systems.
  humanURL: https://raft.github.io/
  baseURL: https://raft.github.io
  tags:
  - etcd
  - Leader Election
  - Log Replication
  - Raft
  properties:
  - type: Specification
    url: https://raft.github.io/raft.pdf
  - type: Documentation
    url: https://raft.github.io/
  - type: Reference
    url: https://thesecretlivesofdata.com/raft/
  x-features:
  - Strong leader simplifies log replication
  - Randomized election timeouts
  - Membership changes via joint consensus
  - Snapshotting for log compaction
  x-useCases:
  - etcd, Consul, CockroachDB, TiKV, MongoDB replica sets
  - Replicated key-value stores
  - Configuration management for orchestrators
- aid: consensus:pbft
  name: Practical Byzantine Fault Tolerance (PBFT)
  description: PBFT, by Castro and Liskov (1999), is a Byzantine fault-tolerant consensus protocol that tolerates up to f
    Byzantine failures with 3f+1 replicas. PBFT influenced subsequent BFT protocols including Tendermint and HotStuff.
  humanURL: http://pmg.csail.mit.edu/papers/osdi99.pdf
  baseURL: http://pmg.csail.mit.edu
  tags:
  - BFT
  - PBFT
  properties:
  - type: Specification
    url: http://pmg.csail.mit.edu/papers/osdi99.pdf
  - type: Reference
    url: https://en.wikipedia.org/wiki/Byzantine_fault
  x-features:
  - Tolerates Byzantine (arbitrary) failures
  - Three-phase commit protocol (pre-prepare, prepare, commit)
  - Foundation for many blockchain BFT consensus algorithms
  x-useCases:
  - Permissioned blockchains
  - Hardened configuration systems
  - Research baseline for new BFT protocols
- aid: consensus:tendermint
  name: Tendermint / CometBFT
  description: Tendermint (now CometBFT) is a Byzantine fault-tolerant consensus engine that powers Cosmos SDK chains. CometBFT
    decouples consensus from application logic via the Application Blockchain Interface (ABCI), allowing custom blockchain
    applications in Go, Rust, and other languages.
  humanURL: https://docs.cometbft.com/
  baseURL: https://docs.cometbft.com
  tags:
  - ABCI
  - BFT
  - Blockchain
  - CometBFT
  - Cosmos
  properties:
  - type: Documentation
    url: https://docs.cometbft.com/
  - type: GitHubRepository
    url: https://github.com/cometbft/cometbft
  - type: Reference
    url: https://docs.cometbft.com/main/spec/consensus/consensus.html
  x-features:
  - Round-based BFT consensus with leader rotation
  - ABCI protocol decouples consensus from application
  - Instant finality on commit
  - Powers Cosmos Hub, Osmosis, and other Cosmos SDK chains
  x-useCases:
  - Building permissioned and permissionless blockchains
  - Custom application chains in the Cosmos ecosystem
- aid: consensus:hotstuff
  name: HotStuff
  description: HotStuff is a leader-based BFT consensus protocol with linear view change and three-chain commit, designed
    by Yin et al. HotStuff is the foundation for Diem/Libra BFT and inspired modern protocols like Aptos AptosBFT and Sui's
    Mysticeti.
  humanURL: https://arxiv.org/abs/1803.05069
  baseURL: https://arxiv.org
  tags:
  - BFT
  - HotStuff
  - Linear
  properties:
  - type: Specification
    url: https://arxiv.org/abs/1803.05069
  - type: Reference
    url: https://github.com/hot-stuff/libhotstuff
  - type: Reference
    url: https://github.com/aptos-labs/aptos-core
  x-features:
  - Linear view change (O(n) message complexity)
  - Three-chain commit rule
  - Optimistic responsiveness
  - Foundation for Diem, Aptos, Sui consensus
  x-useCases:
  - Modern blockchain consensus designs
  - High-throughput, low-latency BFT systems
common:
- type: Reference
  url: https://en.wikipedia.org/wiki/Consensus_(computer_science)
- type: Reference
  url: https://en.wikipedia.org/wiki/Paxos_(computer_science)
- type: Reference
  url: https://en.wikipedia.org/wiki/Raft_(algorithm)
- type: Reference
  url: https://en.wikipedia.org/wiki/Byzantine_fault
- type: Reference
  url: https://groups.csail.mit.edu/tds/papers/Lynch/jacm85.pdf
- type: Resources
  url: https://raft.github.io/
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com