The Optimization Playbook: 7 Fixes That Reduced Response Time by 83%

In Part 3 we identified the exact bottlenecks — a plugin adding 4x meta joins, 236 duplicate queries, missing indexes, and WPML overhead. Now it was time to fix them. Here are the 7 specific optimisations that took response times from 20+ seconds down to 3.6 seconds.

Our optimisation strategy

Before touching anything, we established five rules:

• Measure everything — K6 load test before and after every change
• One change at a time — never stack changes, you won’t know what worked
• Biggest impact first — high impact, low effort goes first
• Document everything — baseline metrics, change made, result
• Have a rollback plan — database backup before every change

Fix 1: Remove WC Global Product Order plugin

This plugin caused 75% of the performance problem by adding 4x postmeta JOINs to every product query. First we verified how many products were using custom ordering, exported the data, then deactivated the plugin and switched to WooCommerce’s built-in popularity ordering — which uses an indexed meta field:

-- Check how many products use custom ordering
SELECT COUNT(*) FROM wp_postmeta
WHERE meta_key = '_wc_gpo_custom_order';

-- Deactivate via WP-CLI
wp plugin deactivate woocommerce-global-product-order

// Switch to built-in popularity ordering (already indexed)
add_filter('woocommerce_default_catalog_orderby', function() {
    return 'popularity';
});

Fix 2: Add critical database indexes

Always back up first, then add indexes to the most queried columns:

-- Backup first
wp db export backup-before-indexes.sql

-- postmeta indexes
ALTER TABLE wp_postmeta ADD INDEX idx_meta_key (meta_key(191));
ALTER TABLE wp_postmeta ADD INDEX idx_post_meta_key (post_id, meta_key(191));
ALTER TABLE wp_postmeta ADD INDEX idx_meta_key_value (meta_key(191), meta_value(50));

-- WPML translation indexes
ALTER TABLE wp_icl_translations ADD INDEX idx_element_id (element_id);
ALTER TABLE wp_icl_translations ADD INDEX idx_element_lang (element_id, element_type(50), language_code(10));
ALTER TABLE wp_icl_translations ADD INDEX idx_trid_lang (trid, language_code(10));

-- WooCommerce product lookup indexes
ALTER TABLE wp_wc_product_meta_lookup ADD INDEX idx_product_id (product_id);
ALTER TABLE wp_wc_product_meta_lookup ADD INDEX idx_stock_onsale (stock_status(20), onsale);

Fix 3: Install Redis object cache

Redis stores query results in memory so duplicate queries don’t hit the database. This directly targets the 236 duplicate queries we found in Part 3.

# Install Redis server
sudo apt-get install redis-server
sudo systemctl enable redis-server

# Install WordPress plugin
wp plugin install redis-cache --activate

// Add to wp-config.php
define('WP_REDIS_HOST', '127.0.0.1');
define('WP_REDIS_PORT', 6379);
define('WP_REDIS_PREFIX', 'yoursite_');
define('WP_REDIS_COMPRESSION', true);
define('WP_REDIS_MAXTTL', 86400); // 24 hours

# Enable and verify
wp redis enable
wp redis status

Fixes 4–7: The remaining gains

Cumulative results after all 7 fixes