Ajax call is blocking the entire UI

HI all,

I have created a component that is used to load a badge count. I am
updating this component every 5 seconds, however the processing for some
environment takes longer due amount of data. There fore, the ajax call
request done in this component was just blocked the entire UI avoiding any
other request while the ajax call is not returned. I solved that problem by
creating a thread to run my background process, and immediately return the
request, next time a new request is done I check if the work by thread is
done and update my UI. Nevertheless, I am still wondering why an ajax
request that is supposed to be asynchronous is blocked the other requests.

Regards,
Rob