Thanks for the feedback. Yes, it is normal for the size of the database to increase when adding keys. It’s the oldest tradeoff in computer science: space vs. time. Adding keys saves time by adding space.
You’re running Query Monitor. It’s best to deactivate it in production because it imposes some overhead.
Your uploaded monitors show me that your MySQL server has 1GiB of buffer pool RAM, and that it is 91% full. That’s not much buffer pool for a site like yours with about 74K products+posts+pages and 14k registered users.
Your site has a lot of options. Is it possible to get rid of ones you no longer use?
And, it appears, from the queries in your monitors at any rate, that your performance problems are not due to complex queries of products, but rather simpler operational stuff like options and action scheduler (cron) work. So, my suggestions.
- Add a persistent object cache plugin if you can.
- Increase the amount of RAM available for the innodb_buffer_pool_size in your database server. If you’re using a budget hosting service, it may be time to move to a faster service.