If have the following situation:

I'm using a gallery slideshow. The presenter logs in and starts flipping through. The guests login separately. However, when the presenter clicks to view the next slide, the guests slide should automatically turn to that slide as well.

I have thought about using a setInterval to check the server every ten seconds. However, this would put a good amount of burden on the database server, especially when there are more than six guests.

1 - Am I right that it would put a great deal of burden on the database server?
2 - Is there a better way of going about this?

Please let me know your thoughts