Hi Everybody!

I'm trying to diagnose a very strange performance problem and I've reached a point where I can't figure out what's actually happening.

The site runs on WordPress and uses the SmartMag theme. I bought the theme for around $100, but unfortunately my support period has already expired.

The weird part is that after a lot of testing, the evidence keeps pointing back to SmartMag itself, which doesn't make much sense because it's a very popular theme with thousands of installations.

Here's what I've tested so far:

Switched to a default WordPress theme → performance becomes excellent. Switched back to SmartMag → performance degrades dramatically under concurrent load. Disabled every single plugin. Disabled SmartMag Core. Disabled WP-Cron. Checked OPCache. Checked MySQL performance. Checked autoloaded options. Checked custom code in functions.php. Query Monitor doesn't show any obviously slow SQL queries.

Some numbers:

Default WordPress theme

-50 concurrent users -~28ms average response time -Handles the load without any issues

SmartMag (all plugins disabled)

-50 concurrent users -~12-20 seconds average response time - Massive slowdown

I also created a simple test page with almost no content and the problem still exists.

Even more interesting: when testing a file that only loads WordPress via wp-load.php, I sometimes see execution times around 0.2 seconds, but under load it can occasionally jump to 5-6 seconds.

This makes me think the problem happens somewhere during WordPress bootstrap or theme initialization rather than during page rendering.

At this point I'm not trying to blame the theme. Since SmartMag is widely used, I'm assuming either:

I'm missing something obvious, There's a known SmartMag bottleneck, Or there's some interaction between SmartMag and my hosting environment.

Has anyone seen similar behavior with SmartMag or other large magazine/news themes?

What would you investigate next? Which hooks, theme initialization routines, or profiling tools would you focus on to find the exact bottleneck?

Any ideas would be appreciated because right now I'm running out of things to eliminate.