https://githubengineering.com/mysql-testing-automation-at-github/

MySQL infrastructure is a critical component to GitHub. MySQL serves GitHub.com, GitHub’s API, authentication and more. Every git request touches MySQL in some way. We are tasked with keeping the data available, and maintaining its integrity. Even while our MySQL clusters serve traffic, we need to be able to perform tasks such as heavy duty cleanups, ad-hoc updates, online schema migrations, cluster topology refactoring, pooling and load balancing and more. We have the infrastructure to automate away such operations; in this post we share a few examples of how we build trust in our infrastructure through continuous testing. It is essentially how we sleep well at night.