How to remove inactive threads in mysql?

Question

MySQL

I have a server with about 10 sites, and a lot of data in the database, a lot of requests for both writing / updating and reading.
Question two.
1. On one of the servers I saw this picture:

It looks like this for me

(the screenshot was taken after the server was rebooted
) as I understand it, on this server, after a query is made to the database, the mysql thread is killed. And I have some threads live forever. I don't think this is good.
Can you tell me if this is the case and how to achieve this?
2. Can you recommend a good article/video/service for setting up mysql?
PS In general, the main problem of my server is that mysql, when performing unloading goods or similar (heavy) operations, takes all the processor resources.

Answer 1

Do you know about the connection pool? Do you have anything holding the persistent pool to the muscle? If so, then this is just right, rather than opening and closing connections every time.
And they cannot live forever. By default, the muscle terminates inactive connections older than 8 hours.

Answer 2

This is good and right.
Limit mysql resources in config.
Well, hire an admin to optimize your server and mysql.