A discussion of how we handle upgrades to major new versions of MySQL and the challenges we have to do this at scale.

Upgrading to MySQL 8.4 at Booking.com - why we want to do this? why NOT stay on 8.0? - how to approach the process with a large fleet - changes around automation and tooling - testing of the changes and deployment - compatibility issues - new features? - In many ways 8.4 is to allow us to test 9.X --> Why should we care?