I'm waiting for a CI build as I write this - If I ran it locally it would take 3 hours, but the CI system can split across multiple AWS nodes and so be done in 25 minutes (the time of the longest build). I tried getting a more powerful machine, turns out my build becomes memory bandwidth bound at about 48 cores (building on a RAM disk makes the build take longer which is how I know it is memory bandwidth).
In my case, it would take about 45 hours to run on a single machine. Our distributed testing infrastructure gets it done in about 2. But there's a limited amount of machines, so you usually have to add 2 more hours queuing to that.
