TL;DR: Redis is an AP system, not a CP system. It cannot guarantee strong consistency. For high-concurrency use cases, expect potential data races when using Redis. Consider systems that provide strong consistency (e.g., etcd, ZooKeeper) if you need strict guarantees.

The Single Instance Lock

In the previous post, we explored how to implement a distributed lock using a single Redis instance. We addressed the question: what if the client crashes? But we left one critical question unanswered: what if Redis itself fails?