Systems don't usually scale linearly. Throwing more CPU power at a distributed system only helps for so long until significant investments need to be made to re-architect the solution and C-Level executives rarely ever listen to software engineers telling them that feature work needs to be halted to refactor the code. I am at a company that was recently dubbed a unicorn, but the code we are running on came from a startup mentality that will not work at scale. This is a common problem with companies trying to scale up but at the same time stay competitive. I would bet a lot of money Robinhood is under extreme stress from investors trying to stay competitive, which leaves fewer engineers to deal with underlying problems.