System design interview question
"Design a distributed lock service — something like Chubby or ZooKeeper. Clients across a fleet acquire locks to coordinate: leader election, exclusive access to a resource, configuration that everyone must agree on. It must be correct even when nodes fail and networks partition."
consensus and the limits of distributed locking. The single most important signal is whether the candidate knows that a distributed lock does not guarantee mutual exclusion on its own — a client can hold a lock, get paused or partitioned, and have its lease expire while it still believes it holds the lock. The fix is fencing tokens, and candidates who do not raise this have a dangerous gap.
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