I haven't traced through all the code yet to know the reason, but Hustle does a WP_Query to load EVERY post for every post type when you load the dashboard which is a huge memory issue on large sites with tens of thousands of posts. This happens on line 200 of hustle-module-admin.php. Can this somehow be disabled? Is Hustle unusable on large content sites? The only solution to even load the dashboard is to bump up the PHP execution memory required to 1GB and the max execution time to over 120 seconds in production which is not viable.
If there is no workaround, I'll have to patch the plugin or figure something else out to prevent it from loading the entire wp_posts table into memory.
This should impact any WP site with a ton of posts, but my environment is WP 4.9.8 on a LAMP stack with ~50k posts. Yoast SEO and a few basic post meta fields (done in code, not ACF or another plugin) being the only large customizations loaded.