The two survival structures of market makers and arbitrageurs

Author: @Boywus

In the world of micro high-frequency trading, there have been two long-standing factions: one is the market maker trading that lives off the spread, quoting one leg, usually placing orders in the form of makers, enjoying nominally full capital utilization; the other is cross-exchange arbitrage, aiming for cross-exchange price differences and funding rates, usually taking orders in the form of takers, with capital utilization only nominally half that of market makers;
This article will discuss the characteristics of their risk exposure and elaborate on their differences.

Origin of Risk Exposure

In the world of limit order books, all risk exposure essentially comes from exchanging the power of "controlling time" for the cost of "controlling price."

It can be understood as a free option: when you choose to be the order placer, you gain the right to set the price. You can queue at whatever absolute price you want, but there is no free lunch in this world; in exchange, you give away the choice of "when to execute" or even "whether it will execute" to all market takers for free.

The two major problems that market maker trading needs to solve are "inventory risk" and "fair pricing." After placing an order, if the position is not cleared in the short term, we can regard it as "risk exposure," and in terms of quantity, the risk control system will evaluate it in real time.

When cross-exchange arbitrage uses taker orders, due to the different order placement environments of the two exchanges, such as slippage, disconnections, and tick size rules, it will create incomplete 1:1 hedged exposure.

Transaction Characteristics of Risk Exposure

The fragmentation of market makers comes from the passive discontinuity of order matching. Market makers attempt to provide two-sided quotes, but under the intensive iceberg orders and order-splitting bots in the limit order book, your Bid may be eaten in batches of 0.1, 0.5, or 2.1, while your Ask side remains silent. The fragmentation of market makers is high-frequency and randomly distributed over the timeline, relying on continuous slight price adjustments.

The fragmentation of cross-exchange arbitrage comes from the asymmetry of multi-market rules and matching delays. The exposure is exogenous and actively crosses over, such as tick size rules: if Exchange A requires one BTC per order and another exchange requires ten BTC, this will lead to the formation of "risk exposure" after a transaction on Exchange A, but generally less than ten BTC, ultimately squeezing the hedging instructions.

Exposure Characteristics of Risk Exposure

The opening characteristics of market makers: When a market maker's unilateral Bid is executed to build a position, while the Ask orders remain unexecuted for a long time and the price does not breach the Bid. This indicates that the market is in a healthy mean reversion, and this portion of inventory is favorable, waiting to be closed out on a rebound.

The closing characteristics of market makers: When market makers encounter a unilateral market trend and accumulate a large amount of long inventory, the system attempts to place Maker sell orders to close out through Skewing. If it remains unexecuted for a long time, it indicates that the market's Order Flow Imbalance (OFI) is extremely deteriorating and is accelerating into a crash. At this point, the closing Maker becomes a mere formality, and inventory losses amplify linearly, putting the system at risk of liquidation or forced stop-loss.

The exposure characteristics of cross-exchange arbitrage mainly lie in the engineering aspects:

• Exchange ADL

• Exchange oracle drift

• Exchange funding being artificially interfered with

• Breakdown of the correlation of underlying assets

Relationship Between Risk Exposure and Profit

Both are engaged in a geometric expectation game regarding "execution friction loss" and "residual risk volatility." Systems that obsessively pursue zero exposure will ultimately be worn down by high trading friction.

A truly good structure must allow the system to choose to "let the bullets fly for a while" between cost and risk within a certain time and amount.

Market makers pursue high win rates, high turnover, and low per-trade profits. Market makers enjoy a nominal 100% extreme capital utilization, trading time control for cheap Maker fees and spreads. Therefore, the inventory exposure of market makers directly contributes to excess profits within a certain range.

When inventory does not breach the risk control boundary, the clearing of inventory accompanied by mean reversion yields far more explosive returns than simply capturing a fixed spread on both sides. Market makers exchange "local time passivity" for "long-term probability certainty."

Cross-exchange arbitrage seeks deterministic spatial price differences and structural returns (such as funding rates). Since it primarily takes orders in the form of takers, its nominal capital utilization is cut in half (as it must prepare margin on both sides) and incurs high taker fees.

Thus, the risk exposure in cross-exchange arbitrage (whether from fragmentation due to exchange restrictions or delayed residuals from multi-leg execution) is almost purely a profit loss item. Arbitrageurs tolerate fragmented exposure because they forcibly smooth out small tick fragments using takers, and the slippage costs incurred outweigh the direct risks of holding fragments. Arbitrageurs exchange "capital sunk in space" for "local immediate certainty."

Different Paths to the Same Goal in Micro Order Books

The ultimate evolutionary direction for both is to completely abolish the dogmatic belief in a single order form in micro execution. Whether institutional market makers or mature small retail arbitrageurs, they will ultimately reconstruct the system into a strategy based on a mixed state of cost, delay, and order flow toxicity.

Cross-exchange arbitrageurs will also use the maker model for opening and closing positions to save costs, and in behavior and exposure management, they have highly overlapped with the inventory skewing logic of market makers; market maker trading will execute taker orders under high-risk control system alerts, and various hedging methods will be used for unfavorable inventory, even forming complete lock-ups in extreme cases. Finance is the pricing of risk; they interact with the market in different ways to exchange different return ratios. Market makers sell time, while arbitrageurs sell space—one exposes inventory to the market, while the other sinks capital into the market.
They are all using different forms of risk exposure to exchange for that little bit of thin and cruel certainty from the market.