title: Microservices: how to effectively deal with data dependencies between microservices
body: <p>I am developing an application utilizing the microservices development approach with the mean stack.  I am running into a situation where data needs to be shared between multiple microservices.  For example, let's say I have user, video, message(sending/receiving,inbox, etc.) services.  Now the video and message records belong to an account record.  As users create video and send /receive message there is a foreign key(userId) that has to be associated with the video and message records they create. I have scenarios where I need to display the first, middle and last name associated with each video for example.  Let's now say on the front end a user is scrolling through a list of videos uploaded to the system, 50 at a time.  In the worst case scenario, I could see a situation where a pull of 50 occurs where each video is tied to a unique user.</p>
  
  <p>There seems to be two approaches to this issue:</p>
  
  <p>One, I make an api call to the user service and get each user tied to each video in the list.  This seems inefficient as it could get really chatty if I am making one call per video.  In the second of the api call scenario, I would get the list of video and send a distinct list of user foreign keys to query to get each user tied to each video.  This seems more efficient but still seems like I am losing performance putting everything back together to send out for display or however it needs to be manipulated.</p>
  
  <p>Two, whenever a new user is created, the account service sends a message with the user information each other service needs to a fanout queue and then it is the responsibility of the individual services to add the new user to a table in it's own database thus maintaining loose coupling.  The extreme downside here would be the data duplication and having to have the fanout queue to handle when updates needs to be made to ensure eventual consistency.  Though, in the long run, this approach seems like it would be the most efficient from a performance perspective.  </p>
  
  <p>I am torn between these two approaches, as they both have their share of tradeoffs.  Which approach makes the most sense to implement and why?</p>