# Friday, June 06, 2003

While the presentation itself was a bit slow, the content was very interesting.  It was about how Microsoft, Unisys and others built a highly scalable system for use by law enforcement and the public health system to send and receive alerts such as Amber Alerts and public health warnings.  The biggest factor influencing the design was the fact that they control essentially the entire system, from the back end datacenter all the way to the workstation setups.  This allowed them to take advantage of a lot of features not normally available to “Internet” applications.  For starters, they chose a WinForms app on the client side to provide the best performance and richest user experience.  They use .NET remoting (over TCP using the binary formatter) to get the best performance over the network, which also allows them to hook up bidirectional eventing so that new bulletins can be distributed rapidly without poling.  The client app uses MSDE to cached frequently used data like addresses and geographical data.  Each local client can be configured to either communicate with a local hub system, or with the back end datacenter. 

Since they had to accommodate 25,000 installed workstations, and an addressbook projected at 100M users it makes sense to take advantage of some heavyweight code on the client side to get the best scalability.  Overall it was a good example of how to build a really large system, although it depends so heavily on being able to control the whole system that it may not be applicable in very many cases. 

I’ll looking forward to comparing and contrasting with DEV372 (coming up this morning) which is a case study of the London traffic billing system.  More on that later.


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