title: Spring + two data sources - primary and fallback
body: <p>This is what I'm trying to achieve:</p>
  
  <ol>
  <li>I have two databases, both of them have identical schema and contain table X</li>
  <li>Normally I always use the first DB to read data</li>
  <li>Under some condition, I set a flag</li>
  <li>When the flag is set, I first read the entity from the first DB, but when it's not there, I also check the second DB</li>
  </ol>
  
  <p>Could you please tell me, how could I achieve it with Spring?</p>