I spent a few cycles in media buying and later in sell-side ad tech. Please do say what you will about advertising and its effects on the web, but I will say this: it is a world of fascinating tech. As a buyer I experienced janky pacing all of the time across various platforms, because this is a HARD problem. We had to manually adjust campaigns on a daily basis to ensure pacing worked properly. It was common to stop a campaign and overspend by hundreds of dollars while all of the caching spun down.<p>I'm fascinated to see they are running that all on a single node. Its a massive amount of state aggregated from billions of events that needs to be served at extremely low latency, but couldn't it be partitioned somehow??? Google Fi/Spanner and BigTable have certainly been developed to support these issues. I've been trying to dig up what infrastructure powers Google AdX, but I haven't found anything. AdWords seems to be tied to Spanner, but AdX is/was an entirely different beast. In any case I'm quite certain that it isn't running pacing on a single, gigantic node.