title: Best practices to update asynchronously duplicated data in mongodb
body: <p>I am weighing the pros and cons of migrating from a relation SQL database to mongodb for a web application. This for performance issues*.</p>
  
  <p>Storing all object dependencies in the object itself permits <strong>quick "reads"</strong> for displaying data to users. On the other hand, some data are presents in different collections (for example username is in the users collection but also in the comments collection). I am wondering how to deal with updates of this <strong>duplicated data</strong> in order to also have <strong>quick "writes"</strong>.</p>
  
  <p>I would like to avoid dealing with the updates of these duplications <strong>synchronously</strong>.</p>
  
  <p><strong>What are your options for asynchronous updates ? Are there good practices ?</strong></p>
  
  <p><em>My thoughts on this was to rely on a specific mongodb mecanism (which I don't know) or stack the required updates in a memcache/redis/zeromq engine to be played by an independent process asynchronously.</em></p>
  
  <p>(*) <em>My question is not about how to optimize joins, indexes and sql database engines, other posts on SO deal with that.</em></p>