Frequent Batch Auctions

In a continuous limit order book, whoever reacts to new information fastest gets to trade against stale quotes before anyone else can update them, being a millisecond faster than a competitor can be worth real money, which is exactly why firms spend heavily on speed. A frequent batch auction (FBA) is a market design proposed specifically to remove that payoff, by replacing continuous, one-order-at-a-time matching with a rapid sequence of tiny auctions.

Instead of executing each incoming order against the book immediately, an FBA collects orders over a short interval, proposals in the literature have discussed intervals on the order of tens or hundreds of milliseconds, and then, like an opening auction, matches all the orders received in that window at a single clearing price. The next interval starts immediately after, and the process repeats continuously throughout the trading day.

The key design goal is that being a few microseconds faster within a batch interval provides no advantage, because every order in the same batch is treated identically regardless of exactly when within the interval it arrived. That converts speed from a source of continuous, exploitable advantage into something with much lower marginal value, a firm that's a microsecond faster no longer gets to trade ahead of a firm that's a microsecond slower, since both land in the same batch and get the same price. Some real-world venues have adopted a version of this idea; several European periodic auction books batch executions over short randomized windows for similar reasons, though most major exchanges still run primarily continuous books.

Worked example. In a 100-millisecond batch window, three orders arrive: a buy at $50.03 that arrived first, a sell at $50.01 that arrived 40 milliseconds later, and a buy at $50.02 that arrived last, one millisecond before the window closes. All three are matched together at whatever single price clears the batch, the last order's near-instant arrival relative to the others gives it no pricing advantage, unlike in a continuous book where being first in line to hit a stale quote could matter enormously.