类似于朋友圈，当大量用户拉feed时，是不是需要一个缓存来放置最新的数据呢？ 应该选择Redis 还是Memcached 呢？ 如果选择redis，是不是不能和mongodb放在同一个服务器上？ “if you put MongoDB and Redis on the same box and MongoDB data do not fit in memory, MongoDB will “steal” memory to Redis via the OS paging mechanism. The consequence is a major performance drop for Redis.” 缓存里应该存什么？存所有的原始数据吗？？还是只存_id字段之类的？？ http://www.infoworld.com/article/2825890/application-development/why-redis-beats-memcached-for-caching.html http://stackoverflow.com/questions/11218941/architecture-for-redis-cache-mongo-for-persistence