Hack on the MySQL code for fun and profit ! Ever wanted to learn how to add this little piece of functionality that you're missing in MySQL but the codebase seems large and thus intimidating ? Then this talk is for you: we'll enumerate the ways to extend and alter MySQL functionality and will get you started on hacking on the codebase: what the layout is like and where to fund stuff and documentation to support you. We will also review the state of the doxygen project in MySQL 8.0. The talk assumes you'd have working knowledge with C/C++ and algorithms.