Autoptimize “makes optimizing your site really easy. It can aggregate, minify and cache scripts and styles, injects CSS in the page head by default (but can also defer), moves and defers scripts to the footer and minifies HTML”, thank you to the plugin authors they have done a great job in making this plugin available and free for everyone. The plugin is almost perfect but Autoptimize does not have its proper cache purging mechanism, “as this could remove optimized CSS/JS which is still referred to in other caches, which would break your site”.

Autoptimize plugin cache size can grow out of control rapidly before you can notice and that can become a huge problem for your WordPress site. On this post you will find two different approaches to tackle this “issue”.

The code snippet below added to your theme functions .php will limit the Autoptimize cache to 256MB.

Thank you to @rahulpragma to make the below snippet available

 

# Automatically clear autoptimizeCache if it goes beyond 256MB
if (class_exists('autoptimizeCache')) {
    $myMaxSize = 256000; # You may change this value to lower like 100000 for 100MB if you have limited server space
    $statArr=autoptimizeCache::stats(); 
    $cacheSize=round($statArr[1]/1024);
    
    if ($cacheSize>$myMaxSize){
       autoptimizeCache::clearall();
       header("Refresh:0"); # Refresh the page so that autoptimize can create new cache files and it does breaks the page after clearall.
    }
}

This code snippet below added to your theme functions .php will schedule cron jobs to delete the cache every week and month. This code snippet is a bit different from the above this code only cleans up the cache it doesn’t limit the size of it.

<?php
namespace wppress;
class GarbageCollection
{
    public function __construct()
    {
        add_filter('cron_schedules', function ($schedules) {
            $schedules['weekly'] = array(
                'interval' => 604800,
                'display'  => __('Once a Week'),
            );
            $schedules['monthly'] = array(
                'interval' => 2635200,
                'display'  => __('Once a month'),
            );
            return $schedules;
        });
        if (!wp_next_scheduled('wppress/garbage/clear')) {
            wp_schedule_event(time(), 'monthly', 'wppress/garbage/clear');
        }
        add_action('wppress/garbage/clear', [ &$this, 'clear']);
    }
    public function clear()
    {
        if (class_exists('\autoptimizeCache')) {
            /* Clear autoptimize cache once a month */
            \autoptimizeCache::clearall();
        }
    }
}
new GarbageCollection();
?>