Scalability

The web application has two parts: front-end and backend, which can be located on different servers.

The backend server hosts PHP files, which deliver data for the web application.

One or more front-end servers can access a single backend server.

The front-end server hosts static HTML files and script api.js. This allows

• change the design of the application without knowledge of JavaScript, PHP and other technologies,
• cache front-end on client,
• use CDN to load the frontend faster from anywhere in the world.

Default, front-end looks for backend on the same server, in the same directory, but you can specify a different location by using the element

<link id="server" href="http://vaskovsky.net/vtl/sample/en/" rel="preconnect"/>