State Machine Replication
Running the same deterministic state machine on multiple nodes, applying the same commands in the same order. If they start in the same state and see the same inputs, they stay in sync.
What is State Machine Replication?
Running the same deterministic state machine on multiple nodes, applying the same commands in the same order. If they start in the same state and see the same inputs, they stay in sync.
State Machine Replication is a advanced concept that sits in the Distributed Systems Core area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "State Machine Replication" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
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Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
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Related glossary terms you might want to look up next.
Raft
A consensus algorithm designed to be understandable. Uses leader election and log replication. Powers etcd (used by Kubernetes) and CockroachDB.
Paxos
A family of protocols for solving consensus in unreliable networks. Famously difficult to understand but mathematically proven correct.
Consensus
The process of getting multiple nodes in a distributed system to agree on a single value. The foundation of distributed databases and coordination services.