Voxel requires MySQL 8 or MariaDB 10.3 or higher to run properly.
The database system is auto detected during installation.
However, if you decide to change the database system after installation, for example you switch from MySQL to MariaDB or vice versa, then you have to select the new version manually in WP admin ➝ Voxel ➝ Settings ➝ Database.
Once you make the change, you have to recreate the Voxel index tables for your post types in WP admin ➝ Post types ➝ Edit each post type ➝ Filtering ➝ Indexing status ➝ Recreate table and index all posts
In addition to changing database system, you can also control the number of post revisions that are stored in your site using Max revision count (per post) option.