Why didn't they move to MariaDB instead? A faster than MySQL 8 drop-in replacement.
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I wrote a summary of the DDL / table design differences between MySQL and MariaDB, and that topic alone is fairly long: https://www.skeema.io/blog/2023/05/10/mysql-vs-mariadb-schem...
Another area with major differences is replication, especially when moving beyond basic async topologies.