php - What is the best way of using database host?

Solution:

but MariaDB service gets off so

I have no idea what this means.

I was thinking to use remote databases and a CDN server for contents

If you are serving content directly from your database then you will have performance problems. However using a CDN is only going to help if:

1. A large part of your customer base has a long RTT to your server
2. You have already optimized the caching of your content

If 1 is not the case, then you'll get as much benefit running your own cache. If 2 is the case then you're either going to have to fix your caching or enhance your database capacity.

gets over thousands hit per seconds

So what? Depending on the queries and the hardware, that might be a a constraint on your service performance. It might not. Tuning your DBMS and queries might help.

Solution:

• Readonly Slaves can be used to provide 'infinite' read scaling.
• Turn on the slowlog, etc, to find the 'worst' queries to improve on. See http://mysql.rjweb.org/doc.php/mysql_analysis#slow_queries_and_slowlog
• Galera Clustering may provide a small amount of write scaling.
• Combining queries may help some.