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.