title: Android RX need synchronous execution of two different processes
body: <p>In our app we have two asynchronous methods that process received message and updated message. We receive them from server correctly: firstly just message and then updated message. They are processed differently but at the end they come both to update message in database. Problem is that sometimes updated message can be processed quicker than message, thus data will be incorrectly written to database. Updated message will be overwritten by older message.</p>
  
  <p>How I can process synchronously different two observables, controlling their database update by the order they were received from server.</p>