Latest Interviews

Why OCaml

Approximately a decade ago, Jane Street adopted OCaml as its primary functional programming language to secure C-like performance and rigorous type safety while maintaining development conciseness. This strategic choice serves as a filtering mechanism for hiring, attracting highly motivated engineers through a specialized one-month training program that results in a consolidated, high-performing workforce. Although the firm faces ecosystem limitations compared to mainstream languages, the implementation of a single language across its multi-billion-dollar systems enables significant code reuse and shifts the priority from empirical testing to the universal guarantees of static type checking.

Effective ML 2011 Harvard CS51 Part 1

Ron Minsky

Ron Minsky, a technical leader at Jane Street Capital, presented a comprehensive case for prioritizing code correctness and maintainability through strict OCaml design principles that leverage the type system to enforce data invariants and ensure pattern match exhaustiveness. The lecture outlined specific architectural strategies, including mandatory interfaces, uniform naming conventions, and a "reader-over-writer" philosophy, which collectively minimize cognitive load and prevent silent failures in high-stakes financial systems. Additionally, the speaker addressed immediate course logistics by extending the Moogle project description deadline and recommending simple list-based implementations to avoid unnecessary debugging complexity.

Caml Trading

Carl Curry, Ron Minsky

Jane Street Capital, a proprietary trading firm operating in four global cities, transitioned its primary development stack to the functional programming language OCaml to satisfy critical demands for absolute correctness, high performance, and code maintainability. This adoption enables the firm's 35 core developers to leverage OCaml's powerful type system and algebraic data types for static exhaustiveness checks, ensuring the rigorous standards required to process billions of dollars in daily equity trades without error. While the language presents challenges in ecosystem maturity, the firm has actively mitigated these gaps through its Jane Street Summer Project and achieved superior hiring outcomes by attracting engineers skilled in functional paradigms.

Seven Implementations of Incremental

Incremental is an internal OCaml library that efficiently refreshes large computations by modeling logic as a dependency graph, allowing localized updates when only small data subsets change. Through eight iterative development phases, the team resolved critical academic limitations regarding garbage collection and dynamic graph restructuring, culminating in a production-ready V8 implementation that achieved a threefold speedup using generalized algebraic data types. This technology successfully transformed a slow trading system frontend into the suite's fastest application and is now being explored for reactive JavaScript compilation and efficient functional data structure diffing.

Public Health, Medical Research and the Cancer Moonshot: A Collaboration to Change the World

Michael Milken, Francis Collins, Linda Fried, Robert Hugin, Freda Lewis-Hall

Vice President Biden and medical leaders are launching a strategic "Cancer Moonshot" to overcome siloed research through a $680 million federal investment and the Precision Medicine Initiative's enrollment of one million Americans. The framework prioritizes seven key themes, including early detection blood tests, single-cell analysis, and public-private partnerships modeled after the Accelerating Medicines Partnership, while explicitly warning against overpromising a timeline for a universal cure. Parallel to the National Institutes of Health and FDA funding, the initiative integrates public health science to address prevention drivers and leverages global data collaboration to accelerate the shift toward data-driven, individualized cancer therapies.

Public Health Summit Dinner March 2, 2016

Mike Milken, Tom Frieden, Rob Califf, Fred Upton, Nancy Pelosi, Francis Collins

This event featured key figures including Francis Collins, FDA Commissioner Rob Califf, and CDC Director Tom Frieden discussing critical public health challenges such as the implementation gap between knowledge and action, rising opioid overdose deaths, and the threat of a post-antibiotic era. The proceedings highlighted specific policy responses ranging from Mexico's successful food taxes and "health stops" to the U.S. House passing the 21st Century Cures Act and funding the Brain Initiative, alongside clinical breakthroughs in treating depression and heart failure. To address these systemic issues, officials urged for robust funding, the adoption of global "find, stop, prevent" strategies, and a massive volunteer effort for the Precision Medicine Initiative to accelerate biomedical discovery.

The Promise of Public Health

Mike Klowden, Richard Besser, Nancy Brown, Thomas Farley, Joseph Jimenez, Fred Upton

The Milken Institute's inaugural Public Health Summit convened key industry and government leaders, including Novartis CEO Joe Jimenez, CDC Director Tom Frieden, and Congressman Fred Upton, to advocate for elevating disease prevention alongside medical cures. Participants analyzed critical strategies such as conditional reimbursement models, real-time data utilization, and the "21st Century Cures Act" to address looming challenges posed by an aging global population and stagnant biotech venture capital. The consensus emphasized that sustainable health outcomes require shifting from volume-based treatment to outcome-based policies that integrate genomics, behavioral interventions, and bipartisan legislative support to bridge significant disparities in US public health metrics.

Infectious Diseases: Staying One Step Ahead

Michael Gerson, Michael Kurilla, Vanina Laurent-Ledru, Pranav Shetty, Moncef Slaoui

Experts including Vanina Laurent Ledru of Sanofi Pasteur and Monsef Slaoui of GSK advocate shifting global health strategy from reactive outbreak response to proactive prevention to counter drivers like climate change and increased mobility. Leveraging platform technologies and industrial-scale manufacturing, the industry aims to bypass the traditional decade-long vaccine development cycle for threats such as Ebola, Zika, and pandemic flu while addressing critical gaps in local infrastructure and surveillance. Despite improvements in specific regions, the panel concludes that long-term consistency in funding and international cooperation is essential to prevent future crises from overwhelming fragile health systems.

A Future of Healthy Aging

Paul Irving, Pinchas Cohen, Linda Fried, Freda Lewis-Hall, Robin Mockenhaupt

A global panel convened to address the critical misalignment between rising life expectancy and stagnant healthspan, framing older adults as an underutilized human capital asset essential for the 21st-century economy. The discussion highlighted that delaying Alzheimer's onset by five years could halve annual caregiving costs and proposed a "Frieden's Triangle" strategy combining genomic risk assessment, social engagement programs, and targeted public health policies to transform prevention. To realize this vision, the group advocated for a "third demographic dividend" through a tenfold increase in federal funding, clinical trial reforms for geriatric populations, and the creation of new social institutions designed specifically for the emerging thirty-year life stage.

The Health of Nations: Meeting the Sustainable Development Goals

Matthew Bishop, David Barash, Stefano Bertozzi, Deborah Birx, Jacqueline Shea

A panel of global health experts and industry leaders convened to evaluate the gap between current Social Progress Index trajectories and the ambitious targets set by the UN Sustainable Development Goals. The discussion highlighted critical failures in data granularity, vaccine development funding, and the unique health crises facing high-income nations like the United States. Experts concluded that achieving these goals requires a strategic pivot from charity-based models to shared-value ecosystems driven by granular data, impact investing, and cross-sector innovation.

Lunch Program │ An Update on Zika Virus With CDC Director Tom Frieden

Tom Frieden, Mike Klowden, Michael Gerson, Lynn Goldman

CDC Director Thomas Frieden and other health experts highlight that public health interventions have driven a disproportionate share of modern economic growth by dramatically extending life expectancy through vaccines, global partnerships, and improved chronic disease management. Addressing current threats like Zika, the speakers emphasize accelerated testing capabilities and the Global Health Security Agenda's accountability framework while contrasting rapid biological changes in life spans with slower genetic evolution. The presentation further illustrates how environmental factors, epigenetics, and escalating portion sizes significantly influence health disparities and disease rates independent of genetics.

Superbugs: Slowing the Spread of Antibiotic-Resistant Bacteria

Maryn McKenna, Beth Bell, Barry Eisenstein, Lance Price, Zachary Rubin

Unchecked antimicrobial resistance threatens to cause 10 million global deaths and $100 trillion in economic losses by 2050, driven by stalled pharmaceutical innovation, agricultural misuse, and rapid pathogen spread. Critical failures in current stewardship and reimbursement models have allowed superbugs like CRE and MCR-1 to emerge, undermining essential medical procedures from cancer treatment to organ transplantation. Urgent interventions including international data sharing, regulatory incentives for novel antibiotics, and a shift in clinical and agricultural practices are now essential to prevent a post-antibiotic era.

Big Data, Small Devices: How Technology Is Advancing Public Health

Anna Barker, Helen Burstin, Atul Butte, Eric Friedman, Kyu Rhee

This panel discussion highlighted the explosive growth of global data, noting that internet-connected devices now number 50 billion while genomic sequencing efforts aim to process the health records of 25% of the world's population by 2025. Experts outlined strategic shifts toward predictive, personalized, and preventative care models utilizing IBM Watson and wearable technology to bridge the decade-long gap between research discovery and clinical application. The dialogue concluded by addressing critical challenges regarding data interoperability, digital equity, and the transition from episodic treatment to continuous population-level monitoring through distributed data ecosystems.

Mental Health: A Global Challenge We Can't Ignore

Margaret Anderson, Olga Acosta Price, Pamela Collins, Paolo del Vecchio, Charles Ingoglia

This panel convened experts to address the global crisis where mental disorders cause over 8 million annual deaths and severely limit life expectancy due to systemic resource scarcity and stigma. Researchers and policymakers highlighted the shift toward neurodevelopmental and immunological models while stressing that 75% of children with needs remain untreated because of misaligned funding and fragmented care delivery. The discussion concluded with urgent calls for legislative action, including the proposed "Excellence in Mental Health Act," to mandate evidence-based standards and transition payment models toward value-driven outcomes.

Waistlines of the World: An Update from the War on Obesity

Cristina Alesci, Patrick Carroll, William Dietz, Debra Eschmeyer, Jonathan Fielding, David Heber, Bill Dietz

A comprehensive panel analysis reveals that while childhood obesity rates have plateaued, adult prevalence continues to rise driven by socioeconomic disparities and addictive food environments. Experts advocate for multi-layered interventions ranging from sugar taxation and corporate incentive programs to person-first language policies to combat social stigma. Ultimately, the discussion emphasizes that preventing obesity through early childhood education and sustainable dietary shifts is more economically viable than treating the condition later in life.