redfour

A Redis-based binary semaphore implementation using pub/sub for fast async wait, unlike polling-based alternatives. Version 2.2.2 is the latest stable release. Key differentiator: uses Redis pub/sub to notify waiters when a lock is released, making it much faster than polling-based locks. Supports Node >=7.6.0. Ideal for coordinating access to shared resources (e.g., token refresh) across multiple processes or servers.