Coordination & Reliability

Coordination and reliability is about how a distributed system keeps many servers working together as one trustworthy whole. Coordination handles agreement and ordering — electing a leader, reaching consensus (Raft/Paxos), distributed locking, and keeping replicas in sync so nodes don’t act on conflicting truths. Reliability is about surviving failures — replication, failover, health checks, quorums, retries, and idempotency so the system stays correct and available even when machines crash or the network splits. The two are tightly linked: good coordination (a majority quorum, a single leader) is usually what makes reliability possible, since it prevents split-brain and data loss. In short, coordination decides who agrees on what, and reliability decides how the system keeps that promise when things break.