https://insidegovuk.blog.gov.uk/2012/11/28/busting-the-cache-to-see-a-pages-update/

Busting the cache to view an update

The information in this blogpost may now be out of date. See the current GOV.UK content and publishing guidance.

Newly created documents will appear on Inside Gov right away when they are published, at their newly created URL. But all existing pages, including the index pages where new documents will be listed, are cached in the CDN with a default expiry time of 30 minutes.

This means that for business-as-usual publishing, it can take up to a maximum of 30 mins to see a new piece of content appear around the site, and updates to existing documents can take up to 30 mins to be visible to all users.

Here’s the tip. If you want to check something has published successfully before the cache expires, you can do so by appending a query string at the end of any URL. Add a ? followed by a string of random characters and hit return to see an un-cached version of the page.

For example to bust the cache on this page:
www.gov.uk/government/how-government-works

Add a random string at the end like so:
www.gov.uk/government/how-government-works?aksjdk [any random letters will do, but each combination will only work once]

If it’s important that a new document appears all around the site the instant it is published, you should use the ‘scheduled publishing’ feature. This automatically sets the cache expiry time for all related pages to be the exact same time as the document is due to be published, so it will appear right away everywhere it needs to.

Note that, due to the default 30 min cache, you can’t schedule a publishing event for sooner than 30 mins in the future. In other words, you can schedule publishing for a future time provided it is later than 30 mins from now.