Suppose you are staring a startup. You know and like python so you build your MVP in python. 1k to 10k lines later you hire a few extra engineers to help bring

Suppose you are staring a startup. You know and like python so you build your MVP in python. 1k to 10k lines later you hire a few extra engineers to help bring your MVP to a real product. 100k to 1mill lines later you become very very successful and you now have 10s to 100s of engineers coding every day. They're all producing the same number of LOC you were. Maybe more now. Then you take a look at your bills and find that what used to run on a single box on your basement is now costing > 100k/month in compute. So what do you do? Rewrite everything in C++? Well you can start but you have so much software it's hard to do. Maybe you can save a few percent of compute cycles across all of your code? Reduce the 100k/month to 80k/month. Obviously this number is fall smaller than it would be in reality.