Original service method

gistfile1.cs

public User GetUserByEmail(string email)
{
  var key = email;
  var user = Cache.Cache.Get<User>(key);

  if (user == null)
  {
    try
    {
      user = builder.BuildFromNewDbs(email);
    }
    catch (UserNotFoundException)
    {
      try
      {
        user = builder.BuildFromOldDbs(email);
      }
      catch (UserNotFoundException e)
      {
        Trace.TraceError("Something failed because there's not a user with that email.", DateTime.Now, email);

        throw new UserNotFoundException();
      }
    }

    Cache.Cache.Set(key, user);
  }

  return user;
}