Java: use concurrent hashmap or memcached cache

Question

I have a simple country states hashmap, which is a simple static final unmodifiable concurrent hashmap. Now we have implemented memcached cache in our application. My question is, Is it beneficial to get the values from cache instead of such a simple map? What benefits I will get or not get if I move this map to cache?

Answer 1

This really depends on the size of the data and how much memory is you've allocated for your JVM.

For simple data like states of a country which are within a few hundred entries, a simple HashMap would suffice and using memcache is an overkill and in fact slower.

If it's large amount of data which grow (typically 10s/100s MBs or larger) and require frequent access, memcache (or any other persistent cache) would be better than an in-memory storage.

Answer 2

It will be much faster as a HashMap because it is stored in memory and the lookup can be done via the jvm by it's reference. The lookup from memcache would require extra work for the processor to look up the map.

Answer 3

If your application is hosted on only one server then you don't need distributed feature of memcache and HashMap will be damn fast. Stats

But this is not case of web applications. ~99% cases for web applications you host it on multiple servers and want to use distributed caching, memcache is best in such cases.