ATS Hosted Pools: FlexTrade on Broker Opportunities & Challenges

The architecture of equity markets is perpetually evolving, and the latest wave of innovation is generating significant buzz around the rise of "hosted pools" or "private rooms" within Alternative Trading Systems (ATSs). These bespoke liquidity oases are prompting market participants to re-evaluate how and where they seek execution, presenting both compelling opportunities and intricate challenges, particularly for broker-dealers. The article is based on FlexTrade's latest blog. FlexTrade is a global leader offering broker-neutral, multi-asset execution and order management trading solutions.

The Buy Side's Pursuit of Selectivity

At a recent industry gathering focused on ATSs, the buy side articulated a clear need driving their interest in these venues. Hosted pools are viewed primarily as technological conduits, enabling interactions with specific brokers or liquidity providers who may not operate their own dedicated trading platforms. This capability is a key draw. As one head of global trading highlighted, the appeal lies in the ability to more easily measure engagement and the potential for market makers to offer better prices in a bilateral interaction within these controlled environments. It's about finding targeted liquidity and fostering more direct relationships away from the broader market glare.

Broker Control and Bespoke Opportunities

For broker-dealers and other liquidity providers, the allure of hosted pools offered by ATS operators is the granular control they afford. These "side rooms" empower the host broker to segment their order flow with precision, dictating precisely which counterparties are invited to participate in trading interactions. "Segmentation has always been in US equity markets, and participants want to choose who they trade with at different stages of their flow," explained Roman Ginis, CEO of Imperative Execution, operator of the prominent IntelligentCross ATS. He further elaborated, stating that a hosted pool is fundamentally "another means that allows subscribers to control their order flow."

A broker acting as a host within an ATS can tailor the trading environment to their specific needs or those of their clients. This could involve internalizing client orders, setting the matching price at the midpoint of the National Best Bid or Offer (NBBO) or a specified spread, imposing minimum order sizes, utilizing conditional orders, or entirely determining the pool of eligible trading partners. While the overarching rules of the parent ATS generally apply, the host in a private room possesses the flexibility to set "bespoke" rules of engagement, as noted by an electronic market maker active in these pools, stating they "doesn't have to follow the ATS's listed rule set." This level of customization offers brokers a powerful tool for curating liquidity and optimizing execution strategies for specific order types or client segments. Should an order fail to execute within a hosted pool, it can be seamlessly routed to the main ATS or other destinations, and a host can even designate a single order to interact with multiple hosted pools on the same ATS.

Navigating Transparency and Fragmentation

While hosted pools aren't an entirely new concept - they echo the historical "upstairs market" where voice brokers arranged block trades - their resurgence is notable. Part of their current appeal stems from their positioning as an outsourced alternative to building and maintaining proprietary single-dealer platforms (SDPs). For buy-side firms already connected to an ATS, establishing a private room within that existing infrastructure is considerably more efficient than setting up direct connections to numerous individual SDPs.

However, the growth of hosted pools is not without its complexities and challenges, particularly concerning transparency. Given their relative novelty, obtaining a clear picture of the total volume executed within hosted pools across the market remains difficult. While ATSs are required to describe their operations, including hosted pools, in detail on their publicly available Form ATS-N filings with the SEC, the exact volume and composition of participants within these private venues are not readily apparent. An equity market structure expert highlighted the inherent "push/pull on how much transparency an ATS should or should not have," acknowledging the significant disclosure requirements on Form ATS-N while implicitly pointing to areas where greater clarity could be beneficial.

This lack of granular transparency feeds into broader market structure concerns, especially in the context of over 50% of US equity volume now trading off-exchange. With a crowded ecosystem of 20 U.S. stock exchanges and over 30 ATSs, along with single-dealer platforms and wholesale internalized volume, market fragmentation is a persistent topic of discussion. While ATS platforms, primarily used by institutions, accounted for around 12% of market share across 27 platforms recently, and SDPs about 5% across 6 platforms, the surge in off-exchange trading underscores the evolving liquidity landscape.

The buy-side's continued preference for off-exchange venues, including hosted pools, is driven by the need to trade larger sizes without immediately impacting the public "lit" market price or revealing their trading intentions. This pursuit of anonymity and minimal market impact has fueled the demand for innovative ATS models, with some buy-side traders expressing a preference for disruptive approaches beyond traditional price/time priority.

Not all ATSs embrace the hosted pool model. Some firmly believe in an "all-to-all" trading philosophy, arguing that private rooms, while allowing for curated liquidity, may not offer a scalable solution for large institutions. Purestream Trading Technologies, for instance, focuses on a trajectory cross model that provides real-time fills against streaming liquidity by referencing 100% of the overall market volume. Nonetheless, the trend towards specialization within ATSs is undeniable, with various platforms offering unique order types and matching rules. Hosted pools are becoming a vehicle for delivering some of these innovations, with ATSs like Intelligent Cross supporting options such as VWAP crosses within their hosted environments, catering to institutional trading preferences. Navigating this increasingly complex tapestry of trading venues presents a significant task for market participants, requiring sophisticated frameworks to analyze and quantify available liquidity - a process that would benefit from enhanced transparency.

The Evolving Landscape

Looking ahead, the potential trajectory of hosted pools is intriguing. Some market participants see them as a novel mechanism for introducing competition into the retail trading space, particularly in addressing the issue of inaccessible liquidity often routed to off-exchange wholesalers. An electronic market maker suggested that if retail brokers wish to offer midpoint fills to their investors, they could potentially leverage hosted pools with multiple liquidity providers contributing. Roman Ginis indicated that such experiments are already underway, with some brokers observing improved execution quality. The ability for institutions to potentially interact with retail flows is also a compelling prospect facilitated by these venues.

Ultimately, hosted pools are viewed by proponents as more than just a retail-focused development. "This is not just a retail story," asserted Roman Ginis. "This is about best execution and how institutions and broker dealers can gain better control." He concluded by framing hosted pools as another valuable "tool" in the trading arsenal, with the extent of their utilization ultimately determined by the participants themselves. As market structure continues its dynamic evolution, the role and impact of these private liquidity spaces will undoubtedly remain a key area of focus for brokers and the wider financial community.