If you’re the size of GitHub and you’ve been running your infra for years with very little variation in traffic patterns you have a strong incentive to optimise costs for that existing behaviour.
I am afraid thats now how infrastructure works from what I have seen. The number that really matters is QPS. For any system the QPS varies through out the day and across the week and months. Most design considerations easily absorb any 2X increase. Pick up any company and the chances are that the servers are over provisioned, no one takes chances specially with critical components.
What you have going on with Github is mix of multiple things. Traffic alone is not the cause from what little I know, it does adds to the problem for sure
1. Infrastructure is being moved to use Azure, and overall all the cloud providers are struggling with hardware at the moment (same is going on for linkedin too)
2. The core teams, the people who knew the existing systems have either been laid off or moved from Github
3. Microsoft veterans are brought in to fill the gap across the board, they are trying their best but its a lot of unknown for them
How much infra have you seen of the top 100 sites in the world? I've worked on multiple top 10, and absorbing a 2x increase (and the peak is very likely more than 2x) is a very very hard problem that would cause hundreds of pagers to go off and load shedding to very high degrees. There is just not tons of unused capacity lying around in wait at the scale of github. "No one takes chances with critical components" is also very wrong for the simple fact that you don't know which is the weakest link in the chain until it fails.
I have some good experience and I feel bad about state of these things too specially given that a lot of it could have been prevented. What you have here is not a single service, its a system compromised of hundreds of services, possibly without clear ownership for some of them after these many years and reorgs. There is not a single person or group that understands the whole system from technical standpoint and pressure points. It akin to people trying to plug the holes as the water starts getting under pressure from different joints. This duct taping is present in almost all big enough systems, you name them.
> "No one takes chances with critical components" is also very wrong for the simple fact that you don't know which is the weakest link in the chain until it fails.
These companies were built and run by people passionate enough for the craft, ones who cared for the systems, who designed them. There is this idea that you can replace people by process and everyone is replaceable. What you have is a classical state where people are just doing their time.
