In order to implement the responsiveness, the developer did not use the framework, but wrote the custom code to increase the site speed on mobile devices. Other techniques were used for the same reason, e.g., loading images of different sizes for the corresponding screen sizes of devices.
The site backend is built on the Yii framework, which also made it run faster. Unlike the ready-made CMS, the framework has no extra functionality, which significantly makes the work of the content manager simpler.
The site runs on PHP 7.0 and uses a secure connection with the https protocol.