title: Is two-way referencing more efficient in Mongo for a 1 to N relationship?
body: <p>I have a discussion at work about two-way referencing in a 1 to N relationship. <a href="https://www.mongodb.com/blog/post/6-rules-of-thumb-for-mongodb-schema-design-part-2" rel="nofollow noreferrer">According to this post in MongoDB blog</a>, you can do it. We wouldn't need atomic updates at all, so no problem there. Following the example in the article, in our case you can only create or delete task but not change the task owner.</p>
  
  <p>My argument is that two-way referencing is probably more efficient for fetching data from both sides, as we will need to display more often the owner with their tasks and less often just the tasks, in different parts of the program. My colleague says there won't be an efficiency gain and the data duplication is not worth it. </p>
  
  <p>Do you have any info about the efficiency of this approach?</p>