tech-ref Archives · Page 25 of 26 · WordPress VIP Documentation

Object cache

The WordPress object cache is the second layer of caching that is encountered by requests that pass through the page cache and are routed to the origin servers. The object cache stores common or expensive operations directly into memory so that subsequent requests can quickly access them.

Responsive images

Responsive images are automatically supported by WordPress Core. Image markup will automatically include srcset and sizes attributes for images uploaded to a WordPress site’s Media Library. These attributes enable web browsers to automatically use and display the most suitable image size based on a device’s screen size.

Intermediate images

By default, a set of alternate sizes are generated for images that are uploaded to a site’s WordPress media library. These alternate sizes are referred to as “intermediate images”. WordPress Core defines a default array of intermediate image sizes: thumbnail, medium, medium_large, and large. The pixel dimensions for each of these default sizes can be defined in the Settings –> Media screen of the WordPress Admin dashboard.

Image file behavior

Image files that are located within a site's /uploads/ directory are served by the VIP File System and have several default behaviors.

Working with the /tmp directory

The system temp directory (/tmp) is a local, writeable path on an application's web servers that is most commonly used to perform local manipulations to temporary files.

Working with uploaded files

The VIP File System is read-only, but some methods exist to programmatically access and interact with the media files that are stored there.

WP-Cron

VIP’s cron infrastructure leverages WP-Cron provided by WordPress Core, and cron jobs are initiated and regulated by Automattic’s Cron Control plugin. VIP’s Cron Control provides an optimized SQL table for WordPress Cron events. This approach satisfies the highly concurrent querying commonly seen on VIP sites. Each named event in the queue is handled in parallel with other events, allowing for a large event handling capacity. The VIP cron system orchestrates the activity of the event workers in the different containers, to avoid conflicts with two workers processing the same event.

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