Pingdom search check
If Pingdom can’t retrieve the search results page it means that while GOV.UK may be available, it is not possible to retrieve dynamic content. Assuming that the homepage check has not failed, the CDN is probably OK. It is possible for our main provider (Carrenza) to be down and for us to serve static content from a secondary mirror at a second supplier (Skyscape).
This is not such a critical problem as you might assume, because a large amount of traffic comes direct to static content from external searches and can be served from the mirror. Debug as normal by walking backwards from the users perspective through the stack to find out where the failure is.