Principal Data Scientist, Ads

Sr. Staff Data Scientist - Ads Measurement, Signals, Privacy

Reddit

Reddit is a community of communities. It’s built on shared interests, passion, and trust, and is home to the most open and authentic conversations on the internet. Every day, Reddit users submit, vote, and comment on the topics they care most about. With 100,000+ active communities and approximately 126 million daily active unique visitors, Reddit is one of the internet’s largest sources of information. For more information, visit www.redditinc.com. Reddit’s Ads Data Science team is looking for a Senior Staff Data Scientist to lead the scientific strategy behind Reddit’s ads measurement and signal systems. This role sits at the center of how Reddit proves advertiser value, improves signal quality, builds privacy-aware measurement systems, and connects ads exposure to real advertiser outcomes. As a Senior Staff Data Scientist for Ads Measurement, you will be the principal architect of our technical vision and the driving force behind the next generation of our measurement ecosystem. In a landscape rapidly shifting due to privacy regulations, browser changes, and evolving platform dynamics, you will spearhead innovation across experimental design (incrementality/lift), identity, signals, and privacy-safe 1P/3P measurement. This is a high-visibility, high-impact role requiring a rare blend of deep experimentation & causal inference expertise, strategic foresight, and the ability to influence cross-functional executives and industry standards. You will not just adapt to the changing ad-tech environment, you will redefine how we measure value. RESPONSIBILITIES * Technical Vision & Strategy: Define the long-term data science vision & strategy across ads measurement, signal quality, identity, attribution, and privacy. Establish how Reddit should evaluate advertiser value, measurement quality, and signal utility across first-party and third-party products. * Set the Cross-Pillar Measurement Science Strategy: Define the long-term data science strategy across ads measurement, signal quality, identity, attribution, and privacy. Establish how Reddit should evaluate advertiser value, measurement quality, and signal utility across first-party and third-party products. * Build Trusted Measurement and Evaluation Frameworks: Create rigorous frameworks for validating lift, attribution, identity quality, modeled conversions, signal loss recovery, and privacy-aware measurement. Define ground truth, objective functions, quality metrics, guardrails, and decision frameworks that guide product and engineering investments. * Advance Experimentation and Causal Inference at Scale: Lead the evolution of Reddit’s experimentation and lift methodologies across Brand Lift, Conversion Lift, Split Testing, and emerging measurement products. Improve study quality, reduce bias and contamination, and develop scalable diagnostics for experiment health, feasibility, and interpretability. Partner with Ads Engineering to operationalize complex causal models, ensuring that scientific methodologies are not only accurate but also performant, scalable, and resilient in high-throughput production environments. * Connect Signals, Identity, and Ranking Outcomes: Quantify how signal quality, match rates, identity resolution, modeled conversions, and privacy changes affect bidding efficiency, CPA, ROAS, and advertiser outcomes. Partner with modeling and ranking teams to translate measurement improvements into performance gains. * Guide Privacy-Aware Ads Measurement: Lead a privacy-first measurement paradigm, positioning Reddit as a market leader in trusted advertising by recovering signal utility through compliant modeling. * Create Durable Data Science Infrastructure and Standards: Lead cross-org efforts to define reusable methodologies, dashboards, scorecards, quality metrics, and best practices. Build repeatable systems that improve how Ads DS evaluates launches, monitors regressions, sizes opportunities, and communicates impact. * Influence Senior Cross-Functional Strategy: Partner with senior leaders across Product, Engineering, Sales, Marketing Science, Legal/Privacy, and Ads leadership to shape roadmap decisions. Translate complex scientific tradeoffs into clear business and product recommendations. * Uplevel the Data Science Organization: Mentor Staff and Senior data scientists, sponsor high-impact technical work, and raise the bar for causal inference, measurement science, identity evaluation, data quality, and cross-functional decision-making across Ads DS. QUALIFICATIONS REQUIRED * Advanced degree in Statistics, Economics, Mathematics, Computer Science, Operations Research, Physics, or a related quantitative field, or equivalent industry experience. * 10+ years of industry experience in data science, applied science, economics, statistics, or a related quantitative role. * Deep expertise in ads measurement, experimentation, causal inference, attribution, marketplace measurement, or ads optimization. * Proven track record leading ambiguous, cross-functional, multi-pillar problem spaces with measurable business impact. * Strong command of statistical modeling, experimental design, causal inference, and measurement methodology. * Experience defining metrics, evaluation frameworks, quality guardrails, and decision systems for complex products. * Demonstrated ability to balance long-term strategic vision with hands-on execution of complex technical ideas. * Advanced proficiency in SQL and Python or R.  * Ability to influence senior product, engineering, and business leaders through clear technical judgment and communication. * Demonstrated ability to mentor senior ICs and improve technical standards across a data science organization. * Demonstrated agility in adopting AI tools to amplify your personal output, turning complex methodologies into working prototypes with modern speed and efficiency. PREFERRED * Experience with ads identity, conversion modeling, signal loss, modeled conversions, match-rate optimization, or identity graph evaluation. * Experience with lift measurement, brand lift, conversion lift, incrementality testing, MMM, MTA, or third-party measurement partnerships. * Experience working on privacy-constrained measurement, clean rooms, aggregation, consent-aware systems, or privacy-preserving modeling. * Experience partnering with ranking, bidding, or machine learning teams to connect measurement quality to optimization outcomes. * Familiarity with two-sided marketplaces, auction systems, performance advertising, or advertiser-facing measurement products. * Experience building durable internal frameworks, training programs, scorecards, or methodology standards adopted across an organization. Benefits: * Comprehensive Healthcare Benefits and Income Replacement Programs * 401k with Employer Match * Global Benefit programs that fit your lifestyle, from workspace to professional development to caregiving support * Family Planning Support * Gender-Affirming Care * Mental Health & Coaching Benefits * Flexible Vacation & Paid Volunteer Time Off * Generous Paid Parental Leave     #LI-Remote   Pay Transparency: This job posting may span more than one career level. In addition to base salary, this job is eligible to receive equity in the form of restricted stock units, and depending on the position offered, it may also be eligible to receive a commission. Additionally, Reddit offers a wide range of benefits to U.S.-based employees, including medical, dental, and vision insurance, 401(k) program with employer match, generous time off for vacation, and parental leave. To learn more, please visit https://www.redditinc.com/careers/. To provide greater transparency to candidates, we share base salary ranges for all US-based job postings regardless of state. We set standard base pay ranges for all roles based on function, level, and country location, benchmarked against similar stage growth companies. Final offer amounts are determined by multiple factors including, skills, depth of work experience and relevant licenses/credentials, and may vary from the amounts listed below. The base salary range for this position is: $232,500—$325,500 USD In select roles and locations, the interviews will be recorded, transcribed and summarized by artificial intelligence (AI). You will have the opportunity to opt out of recording, transcription and summarization prior to any scheduled interviews. During the interview, we will collect the following categories of personal information: Identifiers, Professional and Employment-Related Information, Sensory Information (audio/video recording), and any other categories of personal information you choose to share with us. We will use this information to evaluate your application for employment or an independent contractor role, as applicable.  We will not sell your personal information or disclose it to any third party for their marketing purposes.  We will delete any recording of your interview promptly after making a hiring decision.  For more information about how we will handle your personal information, including our retention of it, please refer to our Candidate Privacy Policy for Potential Employees and Contractors. Reddit is proud to be an equal opportunity employer, and is committed to building a workforce representative of the diverse communities we serve.  Reddit is committed to providing reasonable accommodations for qualified individuals with disabilities and disabled veterans in our job application procedures. If, due to a disability, you need an accommodation during the interview process, please let your recruiter know.

Principal Data Scientist

CoMind

At CoMind, we are developing a non-invasive neuromonitoring technology that will result in a new era of clinical brain monitoring. In joining us, you will be helping to create cutting-edge technologies that will improve how we diagnose and treat brain disorders, ultimately improving and saving the lives of patients across the world. THE ROLE: The Data Science team at CoMind develops the algorithms and machine learning systems that transform raw optical interference signals from CoMind One into continuous, clinically meaningful measurements of cerebral blood flow, intracranial pressure, and autoregulation. Working at the frontier of photonics, physiology, and applied ML, the team's work directly determines what CoMind One can measure, how accurately, and under what clinical conditions. As Principal Data Scientist, you will be the technical authority for CoMind's data science function, setting methodological direction for signal extraction and ML modelling, personally driving the most complex and highest-impact problems, and providing expert guidance across the team. This is a senior individual contributor role: you will not manage people directly, but your technical leadership will shape how the entire team approaches its most challenging problems. You will work closely with R&D, Clinical, and Software Engineering. At CoMind, all team members work at least 4 days per week from our new Kings Cross offices, plus a flexible work-from-home day. RESPONSIBILITIES: * Own the technical direction for signal processing and ML model development on CoMind One, defining approaches, architectures, and evaluation frameworks that set the standard for the team * Lead the development and validation of the most complex data science components, from novel algorithm design through to evidence generation for regulatory submissions * Act as the primary technical reviewer and expert resource across the data science team, setting the bar for methodological rigour, reproducibility, and scientific integrity * Drive the design and execution of data collection and labelling strategies with Clinical teams, including ground truth definition, dataset governance, and performance benchmarking * Contribute to CoMind's IP and publication strategy, authoring and reviewing technical papers, patent applications, and regulatory documents * Represent the data science function in cross-functional technical forums, architecture reviews, and external scientific and clinical engagements * Identify and introduce new methods, tools, and approaches that advance CoMind's signal extraction and ML capabilities * AI is fundamental to our culture. It's not just a tool, but a core part of how we work, collaborate, and innovate. We expect all team members to embrace AI in their daily work and continuously find new ways to use it effectively. SKILLS & EXPERIENCE: * 15+ years of experience in data science, ML, or applied research, with a strong track record of independent technical leadership on complex, ambiguous problems * Deep expertise in time-series signal processing and physiological or biomedical ML, including hands-on experience developing and validating models on noisy, real-world physiological data * Demonstrated ability to take algorithmic work from research through to production-quality, validated implementation * Experience in a regulated industry (medical devices, diagnostics, pharma, or similar), with familiarity with algorithm validation and documentation requirements for software as a medical device * Strong record of scientific output: publications, patents, or equivalent evidence of original technical contribution and domain authority Nice to Have * Background in neuroscience, neuromonitoring, neurophotonics, and/or cerebrovascular physiology * Experience with optical signal processing - e.g. LiDAR, pulse oximetry, NIRS, laser doppler flowmetry, or related technologies * Familiarity with FDA regulatory pathways for AI/ML-based medical devices BENEFITS: * Company equity plan so all employees share in the success of the company * Salary-sacrifice pension scheme * Private medical, dental and vision insurance (medical history disregarded) * Group life assurance at 4x annual income * Comprehensive mental health support, including unlimited access to 1:1 sessions with trained professionals * Unlimited holiday allowance (+ bank holidays) and one week of remote working per quarter * Lunch voucher (£10) every day for JustEat and free dinner on those days where you need to work later * Twice weekly deliveries of fresh fruit and an extensive selection of snacks and drinks * YuLife subscription, allowing you to turn your daily steps and meditation into discounts at a range of stores * Access to Udemy for upskilling and professional development.

Principal Data Scientist

Marshmallow

We’re on a mission to make migration easy. We started building Marshmallow in 2017. Since then, we’ve grown from 3 to 700+ people, gained unicorn status, raised ~£140M over three funding rounds, turned profitable, insured millions of drivers and lent millions in car loans. But we’re only just getting started. Our goal is to become one of the largest financial services providers in the world. Over the next 10 years we’ll grow exponentially, not only by scaling our existing products, but also by building new ones. To achieve our goals we need incredibly ambitious, commercially driven people who never settle for ‘good enough’. Marshmallowers are hungry for autonomy and ownership, and would rather improve than coast. Everyone raises standards and has an impact, with a focus on collective success over self-interest. We’ve created an environment where curious, tenacious people win and grow together. If that sounds motivating, this could be the place for you. LONDON (HYBRID, 3 DAYS IN OFFICE) DATA SCIENCE AT MARSHMALLOW Our Data Science team partners across the business to turn data into better decisions, smarter products, and simpler customer journeys. We work closely with Product, Engineering, and Operations to build and ship models and AI systems that are reliable in production and deliver measurable impact. Within Data Science, this role sits in Claims, supporting the function and the broader ambition to automate more of the claims journey. Claims is one of Marshmallow's most important customer touchpoints, and we're looking for a Principal Data Scientist who can provide technical leadership across traditional ML and Generative AI, bring system-level thinking to how we scale decisioning, and confidently challenge proposals to ensure we build robust, sustainable solutions. WHAT YOU'LL BE DOING * Provide technical leadership for data science across Claims Fraud, shaping the approach to risk decisioning and fraud detection in partnership with Product and Engineering * Design, build and iterate on production ML and Generative AI/LLM systems that support claims validation and automation * Collaborate closely with other Claims data scientists to bring system-level thinking to how models, data and workflows fit together, identifying architectural improvements needed to scale decisioning and reduce time-to-production * Be vocal about the platform and tooling investments needed (monitoring, feedback loops, QA) to achieve AI-driven end to end claims automation * Advocate for robust, scalable, and strategically aligned technical solutions in cross-functional discussions, ensuring current systems and infrastructure contribute to the multi-year vision for automated claims handling * Set a high bar for statistical rigour, experimentation and measurement, helping improve how Claims performance and uncertainty are understood and communicated to senior stakeholders WHO YOU ARE * You think in systems: you can connect the dots between data science, engineering, and product to shape scalable solutions that build on each other over time. * You're confident in challenging assumptions and pushing for the right approach, using strong communication skills to influence stakeholders across seniority levels and disciplines with clear, pragmatic reasoning. * You thrive in ambiguity and change, staying resilient and effective during transitions while bringing structure, clarity, and momentum to complex problem spaces. * You're motivated by real-world impact, partnering closely with cross-functional teams to drive meaningful automation and better customer outcomes across the claims journey. WHAT YOU'LL BRING * Significant commercial experience delivering end-to-end Machine Learning solutions, from problem framing and experimentation through to production deployment and ongoing monitoring * Hands-on experience building and shipping Generative AI systems in production (not just prototypes), including evaluation, safety/quality considerations, and integration into customer or operational workflows * Strong statistical and modelling foundation, with experience in risk-based decisioning under uncertainty (e.g., fraud, credit, insurance, or other regulated domains) * Proven ability to influence technical direction across Data Science and Engineering, including shaping scalable model/service integration patterns and challenging proposals to drive robust, long-term solutions * Strong stakeholder management skills, with confidence communicating trade-offs and pushing back constructively with Product and Engineering to ensure high-quality outcomes PERKS OF THE JOB * Bonus scheme designed to reward high performance * Private medical insurance with Vitality, mental health support with Oliva * Personal learning budget and 2 dedicated L&D days a year * Monthly flexible benefits budget to spend as you choose * 25 days holiday plus bank holidays * 4 weeks Work From Anywhere per year We are able to offer visa sponsorship for this position. OUR PROCESS * Initial call with a member from our Talent Team (30 mins) * Past Experience interview with Hiring Manager (60 mins) * Systems Design & Technical interview with a couple of the team (90 mins) * Culture interview (60 mins) Diversity of thought We know the best ideas come from having different perspectives in the room - and we're committed to hiring fairly, regardless of background, identity or experience. If you see yourself in this role, we'd encourage you to apply.