Some interesting tid bits:

* we had to resolve a variety of bottlenecks that appeared faster than expected from moving webhooks to a different backend (out of MySQL)

* * redesigning user session cache to redoing authentication and authorization flows to substantially reduce database load.

* we accelerated parts of migrating performance or scale sensitive code out of Ruby monolith into Go.

I'd like to know what database backend they migrated to. I was also surprised to read that the migration from Ruby to a more performant language had not already been completed. I assume this is because it a large code base with many moving parts, etc.

Another interesting bit: they are hitting performance issues due to the rise of monorepos. GitHub and frankly Git were not designed for monorepos