Why Distributed Locks Are Not the Safety Guarantee You Think They Are

Distributed locks, commonly used in microservices architectures, provide only probabilistic guarantees rather than true mutual exclusion. A real-world incident where a customer was charged three times due to a Redis lock expiring during a JVM garbage collection pause reveals how these systems can silently fail when clocks drift, networks stall, or processes pause unexpectedly, making them fundamentally unsuitable as primary safeguards for critical operations like payment processing.