Financial markets process orders faster than ever before. Although faster speeds are associated with smaller spreads, they may also lead to less informative prices. This column captures this trade-off within a theoretical model of high-frequency trading in modern financial markets. It then uses the model to evaluate some potential market design responses to high-frequency trading that are currently in debate. In particular, it shows that asymmetric speed bumps improve markets by eliminating an inefficient form of high-frequency trading.