title: Using memcache infront of a mongodb server
body: <p>I am trying to understand how mongo's internal cache works and if it does eliminate using memcache. Our database size is around 200G and index fits in the memory but after the index not much free memory left on the server. </p>
  
  <p>One of my colleague says mongo's internal cache will be as fast as memcache so no need to introduce another level of complexity by using memcache.</p>
  
  <p>The scenario in my head is when we read the data from db, it's saved in memcache and next time it's directly read from the cache instead of going back to db server. If the data is changed and needs to be saved/updated, it's done on both memcache server and database server.</p>
  
  <p>I have been reading about this but couldn't convince myself yet. So I'd really appreciate if someone could shed some light on this.</p>