layercache: Stop Paying Redis Latency on Every Hot Read

Every Node.js backend hits the same wall eventually. Your Redis cache is working, latency is acceptable, and then traffic doubles. Suddenly the Redis round-trip that felt like nothing at 200 req/s starts dominating your p95 at 2,000 req/s. You add an in-process memory cache on top, wire up some invalidation logic by hand, and three months later you are maintaining a fragile two-layer system with no stampede protection and no cross-instance consistency. layercache is a TypeScript-first library that solves this problem once, cleanly. It stacks memory, Redis, and disk behind a single unified API and handles the hard parts — stampede prevention, cross-instance invalidation, graceful degradation under Redis failures — out of the box. This post walks through what it does and what the benchmark numbers actually look like on a real Redis backend. The Core Idea your app ──▶ L1 Memory ~0.006 ms (per-process, sub-millisecond) │ L2 Redis ~0.2 ms (shared across instances) │ L3 Disk ~2 ms (optional,