TTFB Won't Go Down? Server-Side Culprits Beyond the Theme

You have taken steps to improve your website's performance, but your homepage still shows a high Time to First Byte (TTFB) according to PageSpeed Insights. The issue lies on the server side, specifically in the origin compute and scheduling. To address this, you should focus on the following aspects of your WordPress and PHP stack:

1. Disable request-driven WordPress Cron and trigger it with system cron at regular intervals (every five or fifteen minutes) instead of on every page view. Audit scheduled events to identify and remove or reschedule unnecessary tasks, such as hourly full-table scans on production. Stagger plugin schedules to avoid shared minutes for backups, analytics aggregation, and link checkers.

2. Implement an off-peak schedule for long jobs, ensuring they run during low-traffic periods in your site's traffic timezone rather than during peak hours.

3. Increase the OPcache memory size and tune the validate_timestamps setting for your deployment flow. Use Realpath cache and adjust the pm.max_children parameter based on traffic to optimize the worker process count.

4. Separate pools for admin, AJAX, and front-end requests when the hosting environment allows it, preventing admin-ajax.php traffic from slowing down public pages.

5. Warm up critical URLs, such as the homepage and top landing pages, after deploying new code. Ensure the same server hosting production workloads does not also run additional tasks like mail sending, staging synchronization, or backup restores, as these can contribute to saturation and slow response times.

By addressing these server-side factors, you can significantly improve your website's TTFB and overall performance without relying solely on front-end optimizations.