How to Build an SMS Service

SMS Interaction Design Considerations > Slow Interactivity

3.4. Slow Interactivity

SMS can be slow. Imagine the heaviest web page you can. Now imagine viewing that web page over a 2,400 baud modem. That, essentially, is the delay you face when waiting for a reply from a text message service. Messages may come back quickly, in a matter of seconds, or you could be waiting for minutes.

Fortunately, user expectations are usually set appropriately by the medium, so you get some latitude, but you still need to minimize the round trips required for an interaction. A user should never have to send a response to a response. If that much interactivity is required, they are likely to put down the phone and seek out a computer (or another service).

Here are some tricks for minimizing round trips:

• Use intelligent defaults: Whatever you think the user will want to do 80% of the time, just do it. Don't ask "are you sure" type questions if you can avoid it.

• Combine steps: Allow the user to include multiple pieces of information or decisions in a single message.