Adding more servers stops being a good option after a certain point. If you're a small company running on 20 servers you can increase your performance by 5% if

Adding more servers stops being a good option after a certain point. If you're a small company running on 20 servers you can increase your performance by 5% if you add just one more. Install it in one day, boom. If you're running on 200,000 servers, a 5% increase is 10,000 servers. That means opening a new building in your data-center, making sure your recruiting team has resources to hire enough staff for it, then hiring that staff, negotiating contracts with the power company, the component suppliers, building permits, hopefully you have enough network capacity otherwise you'll have to expand that too, etc. It's many months of work and a lot more expensive than hiring a handful of engineers to tackle performance and maybe build some libraries in-house.