复盘一次集成测试在 make coverage 阶段卡住的问题：先看到连接池超时，继续排查后又定位到 Lettuce SharedLock 自旋，并整理这次排查路径与修复思路。

A seemingly harmless removal of publishOn(Schedulers.boundedElastic()) led to cascading Redis timeouts in production. This post explains how Spring’s @Cacheable blocks the Netty event loop when used with RedisCacheManager, and why BlockHound failed to catch it.