Scalability Pro speeds up slow SQL queries that run through WP_Query. Whilst Scalability Pro does not directly speed up variations, because it speeds up other areas like WP Admin, it reduces the load on your server and creates more space for your CPU and database to focus on loading variations.
To speed up variations, the best approach is to reduce how many variations you have, e.g. a variation should change the image, otherwise it probably could be a product option instead, and then on top of that use the Redis object cache.
In some cases Scalability Pro can help speed up variations directly – it depends if you have a plugin or theme feature that is performing slow SQL calls when the product variation is fetched.
The main problem with variations is that if you have 4 dropdowns, each with 10 options, then you have 10 x 10 x 10 x 10 variations and all 10000 variations get loaded into RAM by WooCommerce on the product detail page AND on the archive pages.
There will be more WooCommerce product variations optimisations in the future, but for now, the best approach is: Reduce item amount in archive per page, enable your object cache and change product variations to products wherever possible. Take a look here for details about these options.
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