Ideas are ideas, check how WP is reading certain tables and make sure that you have keys for those readings, check if you are storing some kind of garbage and run a process to clean it, frequently, for some process, something that does not change very often, leave it as html code only. (like terms and conditions, about me, etc.)
Ask you Host, how to optimize, all of this may help.

1. Choose a good host
2. Start with a solid framework/theme
3. Use an effective caching plugin
4. Use a content delivery network (CDN)
5. Optimize images (automatically)
6. Optimize your homepage to load quickly
7. Optimize your WordPress database
8. Disable hotlinking and leeching of your content
9. Add an expires header to static resources

You should set up caching, there is no need to serve dynamic content at all times.

Hello
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Check this artical
How to Optimize Your WordPress Database for Better Performance : @ProBlogger

I agree with Petermarker; use a caching solution.
For Wordpress there are several plugins that you can use.

It saves you a lot of time from optimizing the Wordpress performance.

If the site is slow, are you sure it is the Database?

MySQL has an optimization tool in phpMyAdmin, which can be loaded from most hosting accounts through the CPanel. It will show you which tables have overhead and are having issues, and one click to optimize.

I never use cache, although in theory it is a good idea, it is really only needed on very high traffic sites, and can cause more issues with speed and size which can impact your site negatively.