Split Brain

Definitions

1. A failure mode in distributed systems where a network partition causes two or more subsets of nodes to each believe they are the active primary, leading to concurrent writes that diverge and potentially corrupt shared state. Consensus protocols like Raft and Paxos prevent split brain by requiring a quorum (majority) to elect a leader.

   In plain English: When a group of servers loses contact with each other and each half starts acting as if it's in charge, creating conflicting copies of the data.

   Example: "The Elasticsearch cluster went split-brain when the network partitioned — both halves elected a master and accepted writes, so we had to manually reconcile the data."

Related Terms

• CAP Theorem
• Eventual Consistency
• proof of work
• Read Concern
• Replica
• Saga
• Scatter-Gather
• Shared Nothing Architecture
• TLA+
• Zeromq