In MySQL 8.0.18 there is a new feature called new iterator executor for each step. That topic itself deserves its own blog post on how the new iterator executor works, and I will write a post about that as well. But if you cannot wait and you would like to read up, here are some [&]

https://www.percona.com/blog/2019/10/28/using-explain-analyze-in-mysql-8/