govuk-infrastructure: 21. Give Fastly CNAME records a TTL of 300
Date: 2026-10-27
Status
Accepted
Context
GOV.UK uses Fastly as its Content Delivery Network (CDN). Public users don't access GOV.UK servers directly but connect
through Fastly. www.gov.uk is a CNAME record pointing to www-cdn.production.govuk.service.govuk, which is itself a
CNAME record pointing to Fastly.
assets.publishing.service.gov.uk is also a CNAME record pointing to Fastly.
In the event that an incident with Fastly occurs we fail over to our backup CDN by pointing both CNAME records to AWS CloudFront.
Currently, we have set the TTLs for these CNAME records to 1 hour. This means that in the event of an incident with Fastly it will take up to an hour before we can restore service.
Decision
We have decided to give Fastly CNAME records for assets.publishing.service.gov.uk and
www-cdn.production.govuk.service.gov.uk a TTL of 300.
Consequences
As a result of this decision, in the event of an incident with Fastly we will be able to fail over to AWS CloudFront and restore service to users quickly.