Probably not well known but quite an important optimization was introduced in MySQL 5.6 – reduced overhead for “read only transactions”. While usually by a “transaction” we mean a query or a group of queries that change data, with transaction engines like InnoDB, every data read or write operation is a transaction. Now, as a [&]

https://www.percona.com/blog/2018/10/10/instrumenting-read-only-transactions-in-innodb/