Quorum & Consensus in Distributed Systems

Introduction

Consensus protocols are used to ensure that distributed systems agree on a single value or state.

Common Protocols

• Paxos: Classic consensus protocol, hard to implement.
• Raft: Easier to understand, widely used.
• Viewstamped Replication: Similar to Paxos, used in some databases.

Quorum

A quorum is the minimum number of nodes required to agree on a decision.

Use Cases

• Distributed databases
• Leader election
• Replicated state machines

Conclusion

Consensus and quorum are foundational for reliability and consistency in distributed systems.