Techniques of content delivery for HTML content based on a predefined template generated at a content serving service are provided. A request for HTML content is received and a member ID that matches the request is determined to identify a set of campaigns. For each identified campaign, a cache is read to identify respective HTML content. Upon determining that one of the campaigns has corresponding HTML content stored in the cache and that was already generated at the content serving service, a URL is generated based on the request. The HTML content and the URL are sent to a client device. For a campaign that does not have stored HTML content, HTML content for that campaign is generated using a template with a predefined format and content that is specific to the campaign. The template has formatting parameters for the content. The generated HTML content is stored in the cache.