Chubby is a lock service built at Google and described by Mike Burrows in a paper at the USENIX Symposium on Operating Systems Design and Implementation (OSDI) in 2006. Its purpose is to let many clients in a loosely-coupled distributed system coordinate with each other, most commonly to elect a leader or to agree on which machine owns a particular resource.
The paper explains that Chubby provides coarse-grained locking together with reliable, low-volume storage. Clients see an interface that resembles a simple file system: small files and directories that can be read, written, and locked. The design deliberately favors availability and reliability over raw throughput, because coordination decisions are infrequent but must be correct.
Internally, a Chubby cell is a small group of replicas (typically five) that use the Paxos consensus algorithm to keep a consistent, fault-tolerant copy of the lock and file state. One replica is elected master and serves client requests; if it fails, the survivors elect a new one.
Chubby became foundational infrastructure inside Google, used by systems such as Bigtable, and its file-system-like coordination model directly inspired the open-source Apache ZooKeeper.