I worked with application recently which has great memcached hit ratio - over 99% but yet still has average page response time over 500ms. Reason ? There are hundreds memcached gets and even though they have some 0.4ms response time they add up to add hundreds of ms to the total response time.
The great memcached hit ratio is great however even more than that you should target eliminating requests all together. Hit rate is very bad indicator to begin with. Imagine you have application which gets 90 memcache gets (hits) to retrieve some data plus there are 10 more requests which resulted in misses and caused MySQL queries. The hit ratio is 90%. Imagine now you have found a way to store the data which required 90 requests as the single object. You have 1 request (hit) now and 10 misses which drops your hit rate down to less than 10% but performance will likely be a lot better.
The answer in many cases is to use larger objects for the …[Read more]