* Service time expiry

- Replies include "this service expires on".

* Add real Unit Testing.

   - Spec out the system through test harnesses.

      If the tests can run the system, it's complete.

   - Differentiate backends and the independent system.

* Message Queuing

- Process a maximum of X MB over Y requests per unit time Z per
   friend.

- Messages that exceed that maximum are queued for the next time unit.
