Help troubleshooting website performance

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Hi! I ran a WordPress website on a dedicated server (16 GB RAM, 6 CPU, SSD storage) with cPanel.

`WordPress 6.1.3`

`Database: 10.5.21-MariaDB`

`PHP: 7.4.33 (fastcgi)`

`webserver: nginx (reverse proxy) + Apache`

All worked fine for *months*.

Since last week, I noticed very high load (about 30) several times during the day.

No new plugins/themes added.

With “top” I always see `mariadb` process with an high CPU usage, these are the queries I always see:

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MariaDB [(none)]> show processlist;
+——–+————————–+———–+————————–+———+——+———————+——————————————————————————————————+———-+
| Id | User | Host | db | Command | Time | State | Info | Progress |
+——–+————————–+———–+————————–+———+——+———————+——————————————————————————————————+———-+
| 76544 | my_database | localhost | my_database | Query | 0 | Creating sort index | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID
FROM wp_posts
WHERE 1=1 AND wp_posts.post_type = ‘at | 0.000 |
| 79436 | my_database | localhost | my_database | Query | 0 | Creating sort index | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID
FROM wp_posts
WHERE 1=1 AND wp_posts.post_type = ‘at | 0.000 |
| 81672 | my_database | localhost | my_database | Query | 1 | Creating sort index | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID
FROM wp_posts
WHERE 1=1 AND wp_posts.post_type = ‘at | 0.000 |
| 88786 | my_database | localhost | my_database | Query | 1 | Creating sort index | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID
FROM wp_posts
WHERE 1=1 AND wp_posts.post_type = ‘at | 0.000 |

When this happens, nginx/Apache are still up&runnning, but if I try to load the homepage, browse hangs.

If I restart mysql service, problem goes away and website is stable even for several hours.

I’d need some help to find root cause for this high cpu usage.

How do you approach this? 🙂

Thank you!

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