What is Memcache ?

Memcached is a high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.

What is APC ?

APC Cache (Eaccelerator and other similar caches) is Fast but it is not distributed so you’re wasting cache and reducing possible hit rate by caching things locally if you have many web servers. MemcacheD is relatively slow but distributed and so you do not waste memory by caching same item in a few places, it is also faster to warmup as you need only one access to bring item into the cache, not access for each of web servers.

The good thing however is you do not have to select one or another, you can use both at the same time. APC will be great for caching small but frequently accessed things which are not taking too much memory. For example if you store list of states in the database you can cache it this way. For NNSEEK we can use it to cache list of languages, top groups and much of semi-static modules shown on group directory pages. Memcached is good for caching things which take large amount of space combined and which you only need to fetch few per page. For example search results may be good candidate (assuming we want to cache them and want to cache them in memory).

– Linux: memcache.so, apc.so (apt-get install or pecl)
– Windows: php_memcache.dll, php_apc.dll (google to get)