title: How is F1 different from Megastore?
body: <p>Google uses its <a href="http://research.google.com/pubs/pub38125.html" rel="nofollow">F1</a> RDBMS for its Ad Business. Google also has Megastore. My understanding is that they are both built on top of Bigtable. What is the technical justification for having both exist?</p>
  
  <p>Google already offers Megastore on Google App Engine. Would it make sense to offer F1 on App Engine instead of Megastore if not for the existence of legacy use of Megastore?</p>