In Decoupled mode the primary domain points to the Node.js server hosting Frontity. This is the site that visitors access directly in order to view the content.
Frontity will fetch the data from the REST API of the WordPress Server and will return the final HTML as an Isomorphic React App.
Any Frontity architecture requires two servers. In Decoupled Mode you need to have:
A main domain pointing to the Frontity Server, either:
A server running Node.js
A hosted function-as-a-service (FaaS) platform allowing serverless computing, such as AWS Lambda or Netlify functions
A secondary URL (or subdomain) pointing to the WordPress Server, either:
An Apache or Nginx web server running PHP
A hosted software-as-a-service (SaaS) platform with WordPress, such as WordPress.com
In this mode site visitors access the site using the primary domain and are served HTML pages directly from Frontity. The secondary domain is used by content editors to access the WordPress admin pages.
Frontity fetches data from the REST API located on the secondary domain, i.e. the WordPress installation, and uses that information to generate the HTML that is returned to the user.