you need to monitor hit rates for the cached items to see whether most items are being used from cache. If hit rates are very low, then the cache is not buying any performance gains and might actually be slower than not using the cache. Keeping something in cache is a bet that the cost of generating it once, plus the cost of hashing and lookups, is less than the cost of generating it every time it’s needed. If a particular cached object is used only once during the lifetime of a server, then caching it is of no help.
