A cache can enhance database efficiency by reducing the load on the database, but it's not a silver bullet for optimizing overall performance, and its effectiveness depends on various factors such as the frequency of data access, the size of the cache, and the complexity of database queries. Implementing a caching layer in a stack can improve response times for certain operations, but the impact may be minimal when considering all sub-operations involved. In high-intensity applications like fraud detection, AI, and customer 360, where real-time response is critical, sub-millisecond latency is essential to ensure optimal performance. Caching can help with common use cases such as content caching, user session store, and speed up access to backend data stores, but it's crucial to understand its limitations and potential drawbacks in dynamic environments.