Client MySQL: GitHub
"GitHub is a 7-year-old rails app, and unanticipated hot spots and bottlenecks have appeared as the workload's changed over time. The performance schema has been a valuable tool for us, and we can't encourage you enough to check it out for your app too. You might be surprised at the simple things you can change to reduce the load on your database!"
- GitHub: Scaling on Ruby, with a nomadic tech team
- Rearchitecting GitHub Pages
- Workload Analysis with MySQL's Performance Schema
- Making MySQL Better at GitHub