C: Client;
S: Server;
B: Backend;
->C: Hit;
box ..: Server query
{
  box C==C: Generate\nrequest [strong];
  C=>S: Request;
  box S..B: Server gets info
      [color=lgray]
  {
    S>>B: Query;
    S<<B: Response;
  };
  C<=S: Reply;
};

