Redis locks expire after a TTL. If your process crashes, you wait up to 30 seconds for the lock to become available. ZooKeeper takes a different approach: lock it to the session, not a timer. Ephemeral Nodes ZooKeeper has two kinds of nodes: persistent (survive until explicitly deleted) and ephemeral (automatically deleted when the client session expires). A session is kept alive by a heartbeat. If the client crashes, heartbeats stop, the session expires after a configurable timeout, and the ephemeral node vanishes.