In our experience, most performance issues originate from glitches in plugin or theme updates, inefficient code, or a plugin or theme not supporting the latest version of PHP or WordPress. In this article, we’ll make recommendations on what to look for and tools to help you troubleshoot common performance issues on your site.


Check for high admin-ajax.php usage

Make sure Ajax is properly implemented on your site. Plugins are typically (but not always) behind high admin-ajax.php usage. This usually presents on the front of the site and can often be seen in speed test reports.

Another common cause for high admin-ajax.php usage is due to many logged-in users at the same time in the WordPress dashboard triggering the WordPress Heartbeat API to generate frequent Ajax calls.

Check Plugins and Themes

Minimize the number of plugins as much as possible. Make sure remaining plugins are necessary and still supported and updated.

Using your staging environment, you can deactivate all plugins and switch to a default theme. If performance improves, reactivate plugins one by one and reactivate your theme until the performance issue reoccurs. Once you’ve determined which plugin or theme is the source (sometimes it’s a combination of two or more plugins), work with the developer(s), so they can help you resolve the issue and implement the change(s) on your live site.

Transients Manager plugin

If you trace performance issues to an excessive number of transients clogging up your database, the free Transients Manager plugin is an excellent resource for clearing those.

Hire a WordPress Developer or Agency

If you’re not familiar with troubleshooting performance issues, working with a developer or agency to help you track down and resolve issues is recommended.

Troubleshooting Tools

Query Monitor Plugin

The Query Monitor plugin is a free plugin that helps with debugging a number of different areas in WordPress. It can help you track down slow database queries, AJAX calls, REST API requests, and much more. For more details, we have a blog post on how to use the Query Monitor plugin.

Kinsta’s APM Tool

Kinsta’s APM tool helps you identify PHP performance bottlenecks on your WordPress site without having to sign up for third-party monitoring services like New Relic.

New Relic

New Relic is a monitoring tool that gives you detailed performance breakdowns on a granular level. Go to the WordPress > Plugins and themes tab and sort by Most time consuming. This can help show which plugins (or a theme) are associated with the processes that take the longest to complete. Then, go to the Transactions tab to see which specific transactions are most time consuming.

Server Logs

Log files are available in MyKinsta and can also be downloaded via SFTP. These files can be helpful when troubleshooting performance issues on your site.


WordPress has a built-in debug mode to help you track down what’s going on by displaying all PHP errors, notices, and warnings. There are also additional debugging options that can be helpful when investigating specific types of issues.


Xdebug is a PHP extension that can be used with your preferred IDE integrated development environment) in your staging environment to step through your site’s code to troubleshoot issues. To enable Xdebug for your environment, start a new chat with our Support team.

Additional Resources

To take a deeper dive into troubleshooting some common performance issues and other errors, check out these resources: