Apache ZooKeeper is an open-source distributed coordination service designed to manage and synchronize configurations, state information, and communication across distributed systems. It provides a hierarchical key-value store (organized like a file system) to maintain critical data such as configuration settings, node statuses, and leader election details. ZooKeeper ensures high availability and consistency through its replicated architecture, using the ZooKeeper Atomic Broadcast (ZAB) protocol to achieve consensus among nodes.
ZooKeeper supports ephemeral nodes (automatically deleted on session termination) and watchers (notifications for changes), enabling real-time updates and fault detection. Widely used in systems like Kafka and Hadoop, ZooKeeper simplifies complex coordination tasks—such as distributed locking, synchronization, and cluster management—by offering a reliable, atomic, and consistent platform for distributed applications.