I'm setting up an Amazon EC2 server for WordPress and I'm currently caching with APC via the excellent W3 Total Cache plugin.
This is working well but if I want to scale to a load-balanced multi-server setup, it looks like Memcached is the way to go (according to this article: http://sivel.net/2010/11/wordpress-caching-comparisons-part-1/).
This is especially true if I want to use Amazon's ElastiCache system (http://aws.amazon.com/elasticache/), which is protocol-compliant with Memcached.
But my question is about Opcode: as I understand it, APC does Opcode but Memcached does not. So, if I switch to Memcached, how can I still benefit from Opcode? Do I need to run two caching systems (APC and Memcached)? if so, which one do I point W3TC at? Or is there another way?