Storified service method

gistfile1.cs

public User GetUserByEmail(string email)
{
  /*
  *  I use the email param as a key to get a user from cache, 
  *  so I store the email in a variable called "key".
  *  If the user is in cache, we're done! If the user isn't in cache, 
  *  I try to get it from the new database.
  *  If the user isn't in the new database, everything may blow up, 
  *  so I have to be careful just in case it does.
  *  There's no way for me to know whether the user 
  *  is actually there before blowing everything up.
  *  Now, supposing it does blow up, I try to get the user from the old database. 
  *  I still need to be careful because if the user isn't there
  *  everything may blow up as well (it seems this is a very delicate system).
  *  If it does blow up again, the user doesn't exist, 
  *  which means I shouldn't have been called. 
  *  I'll express my anger by throwing an exception to the caller.  
  *  If we're lucky enough, the user was either at the new or the old database. 
  *  We cache it, so that we don't need to get through all of this next time it's needed.
  *  That's it, here's your user, now let me have some rest. 
  */
}