What can be done to reduce the load on the server?

Question

Database

The problem is this, the hosting warns about exceeding the load on the CPU and MySQL, and now the attendance has decreased, and the load has increased.
Tell me how in theory you can solve this problem, where to start? Even how to explain it to a programmer!
For example, we did caching!
And one more thing - maybe this is due to the fact that the wordpress cms has not been updated for a long time?

Answer 1

If there are a lot of plugins, then WordPress is not good.
If caching is already enabled, then you need deep optimization already or moving to VDS
Recently there was a question Excessive account load on the hosting server?
Optimizing Nginx for a Wordpress site with 50k visits per day?
Optimization does not help reduce load

Answer 2

Most likely you are simply squeezed out to a more expensive tariff. After some time, they will run into the new tariff in the same way.
Most likely you need to change hosting.