In terms of do things that don't scale, did they build MapReduce before they had any users? No. They basically made it this far by just building a monolithic product. And they only dealt with this issue when they had to. I think people are always surprised that that's basically all startups do is just turn the water on, fix what's broken, rinse and repeat. That's how big companies get built. But you earn the privilege to work on scalable things by making something people want first.