集成测试卡在 make coverage 阶段，第一眼看到的是连接池超时，真正让进程挂住的是 Reactive Redis 下 Lettuce SharedLock 的自旋，两层问题得分开修。

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.