The Fencing Gap: Why Your Distributed Lock Isn't Safe (and How to Fix It)

You're using distributed locks to protect critical data—but they might be silently failing. A garbage collection pause, a network delay, or a clock skew can allow two clients into your critical section simultaneously, corrupting data without triggering any alerts. This article examines the "fencing gap"—the missing piece that prevents DynamoDB Lock Client, Redis, and ZooKeeper from providing true mutual exclusion out of the box. You'll learn how to detect whether your locks are vulnerable, implement fencing tokens for each platform, and decide when to abandon locks entirely in favor of simpler alternatives like idempotency or database transactions.