I'm running a WordPress site with 500k visitors a month and 150k posts with in average 100 pageviews every second. I am trying to figure out if the load on the server is normal or if there is something I can do to fix the performance issues without increasing the server setup and monthly costs.
Here is the server setup i'm running right now:
- 2 Front-end servers, Nginx: 2 CPU & 4GB RAM
- 1 DB server, MariaDB: 8 CPU & 16GB RAM
- 1 Redis server: 2 CPU & 4GB RAM
The WordPress theme is develop from scratch were I have optimize the queries and minimized the use of plugins (5 plugins in total).
I run Nginx with Reverse Proxy Cache where I cache all pages for 5 minutes to be able to handle peaks in traffic (two daily peaks with 3k visitors in 30 min when sending newsletters).
The MariaDB and Redis server is running Debian with out of the box configuration. The only thing I've changed is innodb_buffer_pool_size = 11G and max_connections = 300 in MariaDB.
The DB CPU is running at 50% when having 100 real time visitors and 85-90% with 300-700 real time visitors.
The problem is that the queries take some time to load (3-6 seconds) even with 50% load at the CPU.
My staging environment is running on the exact same servers but with another database table (same amount of posts) and queries time is 0,5-1,5 seconds.
So the only difference is that the production database have more concurrent users.
What can it be that make the queries take this time to load?