Dynamic data management

Hi

I've a question regarding architecture selection for my project. I need to create something like bwin.com has in live betting. Customers have a page with current options that are changed very fast, admins have a page to change the options. The question is how to implement this to achieve best performance. That's my idea:

Admin has a JSP page with AJAX stuff to add/remove/update things visible on customers side. When he changes anything, it's saved using EJB in db, but also in XML file.

Customers site reads data (every 5 secs, using ajax as well) just from XML file to make sure db is not overloaded. Only when he wants to make an action on given data, double check (with data from db) is made.

What do you thing about this? Is it the fastest solution? Other ideas? Maybe web service for getting data for client?

I think it's very interesting problem, hopefully ranchers will take part in this discussion

Thanks in advance for all tips,
Michal