Fixing GTM4WP Performance Issues: Slow Checkout, Click Delays, and Database Queries

Understanding GTM4WP Performance Issues

Many WordPress users who implement the GTM4WP plugin (Google Tag Manager for WordPress) report various performance-related issues that can significantly impact site speed and user experience. Based on community reports, these problems typically manifest as slow checkout processes, delayed clicks on product pages, and slow database queries that occur during key e-commerce interactions.

Common Performance Problems and Their Causes

1. Slow Checkout and Order Processing

Several users reported checkout processes that slowed down dramatically, taking 20-60 seconds to complete. This appears to be directly related to the "Customer data in data layer" option in the WooCommerce enhanced ecommerce settings. When enabled, this feature triggers complex database queries that calculate customer lifetime value and order history.

The problematic query typically looks like this:

SELECT SUM(meta2.meta_value)
FROM wp_posts as posts
LEFT JOIN wp_postmeta AS meta ON posts.ID = meta.post_id
LEFT JOIN wp_postmeta AS meta2 ON posts.ID = meta2.post_id
WHERE meta.meta_key = '_customer_user'
AND meta.meta_value = '1153'
AND posts.post_type = 'shop_order'
AND posts.post_status IN ( 'wc-processing','wc-completed' )
AND meta2.meta_key = '_order_total'

This query can take several seconds to execute on sites with large order histories, creating a bottleneck during the checkout process.

2. Click Delays on Product Listing Pages

Many users experience 3-8 second delays when clicking products on shop or category pages. This issue is specifically tied to the "Track enhanced e-commerce" and "Cart content in data layer" features. The delay occurs because the plugin is gathering extensive product and cart data before allowing the click action to proceed.

3. External Resource Loading Delays

Some performance issues are caused by external Google resources (gstatic.com, googleadservices.com, doubleclick.net) loading slowly or failing. These external dependencies can block page rendering and create single points of failure for site performance.

Solutions and Workarounds

Solution 1: Disable Non-Essential Data Layer Features

The most effective solution for checkout and click delays is to disable data layer features that you don't absolutely need for your tracking implementation:

1. Go to your WordPress admin dashboard
2. Navigate to Google Tag Manager → Integration → WooCommerce
3. Uncheck "Customer data in data layer" (solves checkout slowdowns)
4. Uncheck "Cart content in data layer" (solves click delays on product listings)
5. Save changes and test performance

Note: The 'GTM4WP – A Google Tag Manager (GTM) plugin for WordPress' team suggests that for basic Analytics tracking, customer data in the data layer is not strictly necessary. Only enable these features if you have specific tracking requirements that demand customer information.

Solution 2: Optimize Database Performance

For sites with large WooCommerce order histories, consider database optimization:

1. Ensure proper indexing on your postmeta table for the _customer_user and _order_total meta keys
2. Regularly clean up old post revisions and transient options
3. Consider using a database optimization plugin to maintain performance

Solution 3: Implement Asynchronous Loading

To address rendering block issues caused by external resources:

1. Consider implementing asynchronous loading for GTM scripts
2. Use a caching plugin that can defer non-essential JavaScript
3. Test with a different GTM container ID (GTM-XXXXX) to determine if the issue is with your container configuration rather than the plugin itself

Solution 4: Evaluate Your Tracking Needs

Carefully consider which enhanced ecommerce features you actually need. Many sites can maintain effective tracking without enabling every available data point. Disabling unnecessary features often resolves performance issues without sacrificing essential tracking capabilities.

When Performance Issues Persist

If you've tried these solutions and still experience performance problems:

1. Use Query Monitor to identify specific slow queries
2. Test with all other plugins disabled to rule out conflicts
3. Check if the issue occurs with a default WordPress theme
4. Monitor your server's resource usage during peak times

Many users have found that selectively disabling certain GTM4WP features provides immediate performance improvements while maintaining essential tracking functionality. The key is to enable only what you need for your specific analytics requirements.