Caching is often misunderstood and can have unintended consequences on system performance. Caching stores selected data in a faster storage medium for quicker access, but it's not a magic solution that automatically improves response times. The effectiveness of caching depends on the cache hit rate, which determines the size of the "green" region in the latency profile. Introducing a cache can increase the likelihood of rare adverse events, elevating latencies at higher percentiles. To achieve meaningful performance benefits, the cache hit rate must be high enough to cover most requests, but this is often not achievable due to the complexity of modern systems and the rarity of certain events. Caches are valuable tools when used strategically, but they should not be relied upon as a sole solution for improving system performance.