There is a special collection of database bugs when the system starts to perform worse when given more resources. Examples of such bugs for MySQL I have: Bug #15815  This is where InnoDB on an 8-CPU system performed worse than on a 4-CPU system with increased concurrency. Bug #29847  This is a similar [&]

https://www.percona.com/blog/2020/09/16/mongodb-4-4-performance-regression-overwhelmed-by-memory/