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Plugin incompatibilities

All WordPress sites on the VIP Platform are provisioned with robust, built-in performance features such as:

Adding third-party plugins that provide additional versions of these features is not only unnecessary, but may result in negative impacts on a site’s performance.

When considering a plugin to add to a site, verify that the plugin is not adding a version of a feature already provided by the platform. In addition, before adding any plugin to a site, complete the steps to evaluate a third-party plugin and its potential compatibility with the platform.

Backup, export, and import plugins

Plugins that are intended to create SQL database and media backups, imports, and exports will not work as expected.

Tooling on the VIP Platform already exists for:

Incompatibilities with the VIP Platform infrastructure have been observed in the following plugins that perform backups, exports, and imports:

Caching plugins

The features offered by caching plugins are already built-in and handled more efficiently by the VIP Platform’s page cache. Third-party caching plugins are not designed to work with the VIP Platform’s globally distributed edge cache servers and auto-scaling server architecture.

Caching plugins can also be incompatible due to

  • Attempts to write files to a cache directory: The VIP File System is read-only.
  • Interactions with an .htaccess file: The .htaccess file only exists on Apache servers; VIP runs on NGINX.

Incompatibilities with the VIP Platform’s caching layers have been observed in the following plugins:

Image optimization plugins

Images uploaded to a site are stored on the VIP File System. The VIP File System automatically serves images that are:

Incompatibilities with the VIP File System have been observed in the following image optimization plugins:

Security plugins

Multiple security measures are supplied by VIP MU plugins for all WordPress sites, including protections for wp-login.php and xmlrpc.php.

All web servers run in read-only mode. This helps to protect applications on the platform against many common forms of attack (e.g. vulnerabilities that allow the installation of backdoor shells and other malicious files).

Incompatibilities with the VIP Platform’s security infrastructure have been observed in the following plugins:

SQL query-intensive plugins

Some plugins generate inefficient SQL queries or can trigger SQL-intensive cron tasks when they are not designed for an enterprise-scale site. Inefficient SQL queries can be compounded if a WordPress site hosts a significant volume of content, if the site is on a large multisite network, if a substantial number of users are registered, or if the application code depends on inefficient meta queries.

On the VIP Platform, cron processes are run in a separate container from application requests, but both share the same MySQL resources. A large volume of simultaneous SQL queries can overload the primary or replica databases, which can lead to an increase in responses with a 503 HTTP status code. Because of this, all SQL queries and cron tasks should be as performant as possible to prevent negatively impacting the site’s responsiveness, especially during planned, or unplanned, high-traffic events.

Plugins that perform file system writes

Plugins that attempt to write files may not always work as expected. Application containers are read-only and attempts to write a file to the local file system will fail.

As an exception, the application container’s system temp directory is writeable. It is commonly used to write and operate on temporary files.

Plugins can also write to the application’s /wp-content/uploads/ directory. Some plugins may use functions or file upload paths that are incompatible with the VIP File System. For details on what file system functions are incompatible please see how to write files to the uploads directory.

Plugins that use the WP_Filesystem API will need additional code for it to function correctly on the VIP Platform.

Example plugins that make file system writes

These plugins are not fully compatible with the VIP Platform. However, they may have filters, actions, or settings that can be used to improve their compatibility. For example, plugins that normally write to the local file system can sometimes be modified via filter to write to the /uploads directory instead. Please consult the plugin’s documentation for more details.

This is not an exhaustive list of incompatible plugins. There may be others. To find out if a plugin is incompatible, look for uses of incompatible file functions.

Plugins that attempt to create intermediate images

Plugins that attempt to create separate, additional versions of an image file (i.e. intermediate images) will not work as expected. These plugins can often be identified by operations that are intended to create versions of a file with an image size added at the end file name (e.g. my-image-300x300.jpg). The 300×300 dimension included in the file name indicates that the plugin expects to have write access, but the File System is read-only.

Site and page builders

Site and page builder plugins—and add-on plugins associated with them—are generally not designed to run on a WordPress site at an enterprise scale. For example, some features in page builders are built with the assumption that there is full write access to an application’s file system. An application’s read-only web containers—and the storage of media files in the external VIP File System object store—can cause some page builder’s attempts to dynamically generate files—such as intermediate images, PHP, and CSS—to fail or cause excess (and expensive) HTTP requests.

Customers may need to modify a page builder’s code to be compatible with VIP’s infrastructure. Be aware that this option may require reapplying modifications whenever the plugins are upgraded to newer versions.

As an alternative to site or page builders, VIP encourages customers to research the many features and capabilities of the Block Editor and Full Site Editing (FSE). The Block Editor and FSE are built into WordPress Core, are highly customizable, and can be fully supported by the VIP Support team.

Advanced Custom Fields

Several security issues exist in the Advanced Custom Fields (ACF) codebase. For WordPress sites with the ACF plugin enabled, it is strongly recommended that several additional steps are taken to improve security, and prevent unexpected issues with performance and functionality.

  • Disable custom fields editing in the WordPress Admin dashboard with the filter: add_filter( 'acf/settings/show_admin', '__return_false' );
  • Register fields via PHP.
  • In ACF version 6.2.7 and later, the ACF the_field() function applies wp_kses() to the field value before rendering to remove unsafe scripts or HTML, but still renders HTML saved in field values. If using an earlier version of ACF—or if the field should not contain HTML or is being used in an attribute or URL—use get_field() with the appropriate escaping function (i.e. esc_html(), esc_attr() or esc_url()) instead.
  • Apply HTML escaping wherever HTML is rendered by ACF.

Because intermediate image sizes are not created as separate files on the VIP File System, fields that interact with images must interact with images based on image ID to retrieve the correct URL.

  • Directly accessing a preferred file size for an image URL with get_field('image')['sizes']['large']; will not work. Instead, access the image by ID and request the size with wp_get_attachment_image_src( $my_image_field['ID'], 'large' )[0] );.
  • Similarly, update_field('image', $image_url, $post_id); will not work, and update_field('image', $attachment_id, $post_id); should be used instead.

Divi

The Divi theme has two known incompatibilities with WPVIP’s infrastructure. Customers have the option to try the suggestions below to resolve the incompatibilities, with the limitation that these suggestions are not kept up to date with every Divi version release. It is the customer’s responsibility to test all setting changes and code modifications on a non-production environment before adding those changes or code to a production environment.

Dynamic CSS

Features related to Dynamic loading (e.g. “Dynamic CSS”) in the Divi page builder theme will not work as expected on the VIP Platform. Enabling these features can also cause degraded site performance. To prevent these issues, navigate to General -> Performance in the WordPress Admin Divi settings screen and disable all features related to dynamic loading.

Writing files

Cache functionality in the Divi theme attempts to write files within /wp-content/, which is disallowed by the read-only VIP File System. To prevent related errors from being generated on sites where the Divi theme is enabled, Divi’s cache functionality is disabled by VIP MU plugins.

Elementor

Several features built into the Elementor site builder—as well as features in some Elementor plugins and extensions—have caused performance issues.

  • Memcached-related performance issues: A significant number of options are autoloaded in alloptions. This results in excessive amounts of time spent processing Memcache calls and can lead to degraded performance
  • Resource-intensive rendering:
    • Content rendering in get_header, print_content, and get_footer components can contribute up to 90% of total transaction time due to a large number of smaller components all making calls to Elementor\Element_Base::print_element.
    • The page builder functionality utilizes sections, and each section is comprised of a large number of deeply nested components. Elementor lacks a caching mechanism for the output rendered by these components. This results in a large volume of component output needing to be re-rendered by the origin server for every page request.

The above performance issues become exponentially consequential if they occur on a site that requires some areas to be served uncached in order to handle authenticated requests (e.g. WooCommerce) or if the application is under heavy load.

Incompatible SVG retrieval operation

Elementor uses the PHP function realpath() to process the path to an SVG file in the WordPress Media Library. Because the VIP File System uses an object store, it lacks a true directory structure. Directory-related operations like realpath() will not work as expected.

Last updated: April 25, 2025

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