Building a High-Performance Cache Layer in Go

Your service is slow. You add Redis. It gets faster. Then Redis becomes the bottleneck -- every request still makes a network round-trip, serialization costs add up, and under load you start seeing latency spikes from connection pool contention. Sound familiar? In this article, we'll build a two-tier cache layer in Go that combines a local in-memory cache with Redis, prevent cache stampedes using singleflight, and discuss the production considerations that separate a toy cache from a battle-tested one. Why Not Just Redis? Redis is excellent. But it's still a network hop away. For a typical service: Operation Latency Local memory read ~50ns Redis GET (same AZ) ~0.5-1ms PostgreSQL query ~2-10ms That's a 10,000x difference between local memory and Redis. For hot keys that get read thousands of times per second, this matters. A local cache also gives you: Zero network overhead -- no serialization, no TCP, no connection pools Resilience -- your service still responds if Redis goes down brie