Every WordPress installation, theme, plugin has its own requirements on server resources. Divi is both theme and plugin in a sense, a collection of an enormous amount of PHP code that works with many files at once and consumes memory accordingly to its size.
Minimum hosting environment recommendations for Divi
According to Divi Help & Support Center
We recommend using the latest stable version of PHP. This will not only ensure compatibility with Divi, but it will also greatly speed up your website leading to less memory and CPU related issues.
By default, memory limits set by your host or by WordPress may be too low. This will lead to applications crashing as PHP reaches the artificial limit. You can adjust your memory limit within your php.ini file, or by contacting your host for assistance. You may also need to define a memory limit in wp-config.php.
Post Max Size limits how large a page or file can be on your website. If your page is larger than the limit set in PHP, it will fail to load. Post sizes can become quite large when using the Divi Builder, so it is important to increase this limit. It also affects file size upload/download, which can prevent large layouts from being imported into the builder. You can adjust your max post size within your php.ini file, or by contacting your host for assistance.
Max Execution Time affects how long a page is allowed to load before it times out. If the limit is too low, you may not be able to import large layouts and files into the builder. You can adjust your max execution time within your php.ini file, or by contacting your host for assistance.
Upload Max File Size determines the maximum file size that you are allowed to upload to your server. If the limit is too low, you may not be able to import large collections of layouts into the Divi Library. You can adjust your max file size within your php.ini file, or by contacting your host for assistance.
This sets the maximum time in seconds a script is allowed to parse input data. If the limit is too low, the Divi Builder may time out before it is allowed to load. You can adjust your max input time within your php.ini file, or by contacting your host for assistance.
This setting affects how many input variables may be accepted. If the limit is too low, it may prevent the Divi Builder from loading. You can adjust your max input variables within your php.ini file, or by contacting your host for assistance.
You can find this information in the WordPress administration area when you log in.
In the admin menu go to Divi > Support Center and look for System Status panel. Green dots mean your configuration is OK, red dots mean you should address it and yellow means you should consider improvements. You are looking for: “Congratulations, all system checks have passed. Your hosting configuration is compatible with Divi.“
Having these settings right should solve your most common hosting problems with Divi user interface, it does not mean your site is optimized for page speed and best performance, these are the common PHP settings that directly influence Divi functionality.