This answer to your question is more about scaling out (many machines) than scaling up (big machines). Many budget hosting providers supporting CMSs like WordP

This answer to your question is more about scaling out (many machines) than scaling up (big machines). Many budget hosting providers supporting CMSs like WordPress and Joomla run very large multitenant MySQL or MariaDB instances. These instances often get into performance trouble when one or more of the customer sites on them grow large or get traffic spikes. The CMSs offer elaborate caching strategies (based on redis, memcache/d) to help mitigate this. But of course the multitenant nature of these instances means that individual customers must configure the caching. And the lowest-end hosting providers don't offer redis or memcache/d. It's possible to monitor various operational parameters (via `SHOW GLOBAL STATUS` and similar SQL statements) to detect problems. It's very hard for customers to mitigate configuration problems (like insufficient buffer pool sizes or too few maximum connections). But customers can change table indexes. Other hosting providers operate large numbers of small separate MariaDB and MySQL instances, one per customer. Considering that WordPress powers something like 30 - 40% of the sites on the internet, the total number of instances is vast. WordPress.org, a vast site, uses multiple read replicas. Version upgrade inertia is a big problem for hosting providers. One provider (whom I will not name) runs a MySQL version that reached end-of-life well over a year ago. New-start MySQL / MariaDB project designs should make provisions for DBMS version updates. Updates are worth applying because the development teams do lots of performance-enhancement work.