Just-in-Time Resale in an Ahead-of-Time Auction for Faster Execution

Abstract

We study Arbitrum's Timeboost auction, an ahead-of-time mechanism that sells a 200ms ordering advantage in an otherwise first-come, first-served transaction ordering policy. The market naturally divides into two phases: a competition phase, in which the dominant searchers compete directly in the primary auction, and a coordination phase, in which they source fast-lane access through Kairos, a Just-in-Time resale intermediary. We use auction bids, time-boosted transactions, and on-chain payment traces to study how well ahead-of-time bids predict realized CEX--DEX arbitrage profits and how the emergence of resale changes surplus allocation. We find that ahead-of-time bids are noisy predictors of short-horizon arbitrage profits. During the competition phase, bid--profit correlations are statistically significant but economically modest at the round level, while correlations increase when profits are aggregated over longer horizons. This suggests that bidders can identify favorable market conditions but face substantial uncertainty about the realized value of any individual one-minute fast-lane interval. After the Kairos transition, competition in the primary auction weakens sharply: in our focused transition-analysis window, paid bids fall from 62.7% of the top bid before the transition to 14.8% thereafter, while total searcher profits remain broadly similar. The resulting dynamics are most consistent with coordination through a common intermediary rather than direct competition in the primary auction. More broadly, our findings suggest that ahead-of-time allocation mechanisms can be vulnerable to secondary-market intermediation when competition among dominant participants is weak.