Why is delivering an ad so complicated? It’s a combination of timely response and personalization. For any given ad, Criteo has less than 50 milliseconds to determine the optimal combination of factors that will induce the consumer to click, create the ad and then deliver it to the correct location; this time bound is due to the fact that most RTB platforms only take into account bids that they receive within 100ms or less, and we need to take into account the network latency as well. The result is a personalized ad delivered for the right price, to the right consumer at the right time. The power behind this process is the Criteo Engine.