caching data with web services

Question

Assume that we are developing a web application that shows currency exchange rates for a bank web site. The rates are stored in an IBM Mainframe in the bank and rates are available through web services. Each time a user accesses the rates page, the page makes a request to the mainframe. This generates too much load on the mainframe. Especially most of the time the rates delivered is the same. How would we design a caching architecture that minimises the trip to the web service. But at the same time rates may fluctuate within the day and if rates have changed the rates web page should not display the cached values but make another request to the web service. How would we design such a caching architecture and make sure it is invalidated on rate changes?

Answer 1

What kind of front end are we talking here? Is it ok to cache data at the UI or do you definitely want to do it in the BL? 

Answer 2

I believe that if you are starting the design of this application, you should consider WCF and not ASMX. You will also get plenty of help in the WCF forum. But anyway, this is a link to the WCF documentation: http://msdn.microsoft.com/en-us/library/ms735119.aspx, and this is a link to a set of WCF samples that will help you with the development of your application: http://msdn.microsoft.com/en-us/library/ms751514.aspx