Resume

T.J. Gaffney

This page contains employment and education details. For non-work projects, see the rest of the site. (Some substantial projects may be excluded due to proprietary information.)

Email: gaffney.tj@gmail.com

Work History

Sr Machine Learning Engineer - Meta (December 2022 - 2025)

I worked on Omnichannel Optimization, which attempts to maximize conversions from multiple channels (online, in-app, offline).

Omni-shopping model

- Developed the first prototype model for targeting omni-shoppers, delivering strong offline results that justified advancing the model to online experimentation.
- Played a key role in launching a new model to 11 alpha advertisers by ensuring campaign QA, historical data availability, system enablement, and measurement frameworks were in place. It was later rolled out to a $300M+ product.

2022-2025

Incrementality

Developed an incrementality estimation and bidding approach using experimental lift data and an ensemble of conversion models, iteratively validating and tuning via backend tests to achieve a 10X lift in estimated incremental conversions.

2022-2025

Omni measurement

- Built a custom analysis workflow for omni-shopping backend experiments, enabling statistically rigorous evaluation of offline conversion lift at scale, supporting 4-8 experiments per month, and saving significant analysis time while accelerating model improvements.
- Unblocked statistically significant experimentation for an offline model by correcting measurement issues, expanding eligible traffic (~2.5X), and designing a fallback holdout approach, ultimately enabling the first valid results and supporting general rollout.

2022-2025

Sr Machine Learning Engineer - Reddit (June 2021 - October 2022)

I worked on Reddit's User Understanding team, whose main task was to features for use in models, primarily recommendations. I created specific features and established patterns for aggregating content features to users and creating user embeddings. This work focused on both batch and streaming pipelines.

User embeddings

Designed and implemented a collaborative-filtering–based user embedding framework with streaming updates to mitigate cold start, enabling effective use in large-scale recommendation and advertising models.

2021-2022

User interests

Engineered scalable user profiling pipeline that aggregated content labels to the user level—incorporating NSFW filtering, label grouping, and temporal decay—delivered via batch (Airflow/BigQuery) and streaming (Flink) systems, with downstream user-to-subreddit mappings powered by approximate nearest neighbors.

2021-2022

Subreddit depth

Built bespoke Markov chain approach to compute average time-to-discover for subreddits. Optimized and parallelized expensive matrix computation for >99% speed up.

2021-2022

Brand safety analysis

Built an analytics dashboard and informed serving pattern changes that increased available ad slots by ~8%.

2021-2022

User covariates

Identified key user-level covariates and built tooling to compute them, improving the rigor and interpretability of A/B test impact analyses.

2021-2022

Software Engineer - Google (May 2018 - June 2021)

I worked on a team called YouTube Brand Connect, which facilitates organic ads in YouTube videos. My role was to build models for predictions and recommendations.

YouTube channel recommendation

Designed and implemented a channel recommendation model to identify the most relevant YouTube channels for a brand based on campaign keywords and URL-derived context. The approach leveraged shared embedding spaces and novel clustering techniques to account for multimodal channel content, paired with a two-stage ranking system optimized for real-time querying at scale. This system reduced channel selection time by ~90%, reproduced expert decisions with >99% precision, and was patented.

2018-2021

Video view predictor

Applied Monte Carlo simulation techniques to estimate aggregate view outcomes for planned video lineups, addressing systematic underprediction caused by outlier effects. The approach enabled reliable percentile-based forecasting, was adopted in a patented solution, and improved planning accuracy for internal stakeholders.

2018-2021

Video review pipeline

Developed a UI-driven pipeline to streamline and automate video review workflows.

2018-2021

Payments database

Implemented a service to support CRUD operations, exports, and reversals for a payments table.

2018-2021

Audience sentiment aggregation

Worked with audience sentiment data to aggregate and analyze signals at the channel level in support of multiple backend initiatives.

2018-2021

Contract processing

I did some side work on a project which attempted to automatically process contracts. For my part, I scraped the FCC EDGAR database to find contracts to be used by human and machine labelers.

2018-2021

Gaming Consultant - The Innovation Group (Apr 2018 - May 2018)

For a brief period, I consulted with The Innovation Group.

Oceans marketing

Leading up to Oceans Casino's relaunch, I prepared some research on the market segments, and designed their loyalty program.

2018

Sports betting market sizing

I conducted surveys and matched to Census data to model demand. I used this in a gravity model to estimate market size of sports betting in states that were considering legalizing.

2018

Manager, Marketing Analytics - Pinnacle Entertainment (Apr 2016 - Apr 2018)

I was a manager in a group that analyzed about $500M of marketing budget; as manager, I drove the direction/workflow. We touched many branches of marketing, including direct mail, host program, events/promotions, loyalty program, and advertising. I worked on a wide range of projects, including: Ad hocs; building reports; A/B split testing of DM campaigns; goal-setting for casino hosts; market segmentation; advertising impacts; and test-analyzing survey results.

Ad hoc analyses and reporting tools

Conducted ad hoc and strategic analyses on marketing effectiveness and consumer behavior (e.g., digital direct mail, Asian play trends, cross-property marketing), delivering executive-ready insights and recommendations.

2016-2018

Data engineering

Integrated and reconciled player and marketing data across multiple source systems, improving data completeness and reliability for downstream analytics.

2016-2018

AB testing of DM campaigns

Advised on statistical methodology and developed software to quickly run AB testing and reporting, resulting in an 80% reduction in process time. Reporting included visualizations for drill down decision-making. Created results repository for long-term trend analysis.

2016-2018

Casino host target model

Redesigned predictions of hosted players' play to improve transparency and interpretability, achieving more accurate identification of high-value players for ~80% of cases and enabling better rewards allocation.

2016-2018

Marketing segmentation

Developed consistent market segmentation methodology across 15 casinos, including spend-per-trip and visit frequency buckets, reconciling differences in underlying metrics to ensure comparability.

2016-2018

Event post forma dashboard

Built a Tableau dashboard to show event KPIs versus benchmarks. Spearheaded initiative and achieved wide roll-out to about 60 users at 15 casinos with 1000s of uses per month, becoming most-used workbook in the company.

2016-2018

Survey analysis

Performed sentiment analysis on year-end survey results, and communicated results to executive leadership.

2016-2018

License bids

Conducted a live game theory experiment to help decide how to bid for gaming licenses.

2016-2018

Actuary, Commercial Lines Analytics - Auto-Owners Insurance (Sep 2014 - Apr 2016)

My team built the models for Auto Owners' commercial line products, including TTP, commercial auto, workers comp, and others. My work was divided about equally into three tasks: Data work, modeling, and research. Data work was SQL work to pull data for our models, and the models were large general linear models.

Fraud model

Used an SVM on text to predict fraud from claim notes. This allowed us to automate the work of 15 FTEs.

2014-2016

Model packet automations

Reversed-engineered pre-packaged GLM software, allowing us to automatically produce modeling packets. This reduced a day-long project to minutes.

2014-2016

Dimensionality reduction

Researched and advised analysts in the company on dimension reduction in auto and credit datasets. We looked into PCA, partial least squares, and lasso regressions.

2014-2016

Lifetime value model

Built a customer lifetime value model of our commerical policy data.

2014-2016

Commercial auto model

Helped refresh our decade-old commercial auto model, combining two previous models.

2014-2016

Presentations

I presented research on Shapley values and family errorwise rates that influenced our modeling techniques broadly.

2014-2016

Stats Lecturer - Davenport University (Jun 2015 - Aug 2015)

I thought Intro to Stats at nights one summer while I was an actuary. That semester I redesigned the term project.

Underwriting Actuary - Qualchoice Insurance (Feb 2014 - Sep 2014)

I was the company's only underwriting actuary. My main job was to create and maintain software to renew group insurance policies. Additionally I worked on a number of small and ad hoc projects.

Obamacare updates

Researched to understand how new legislation impacted the way that we priced policies.

2014

ICD-9 to ICD-10 migration

Wrote a web scraper to get a ICD-9 to ICD-10 crosswalk.

2014

ASO pricing

Priced our new small ASO product using Monte Carlo simulations.

2014

Teaching Assistant - Michigan State University (Sep 2011 - Aug 2013)

While in grad school, I thought a dozen classes over six semesters. These classes included algebra, math for education majors, and calculus 2 and 3. As teacher, I taught classes; met with students; wrote and graded tests; and reported grades. In my first year, I won a reward from the department for teaching.

Education

Master's in Mathematics - Michigan State University (Fall 2011 - Summer 2013)

GPA: 3.83

Qualifying exams

Passed qualifying exams on geometry/topology, algebra, and analysis.

2011-2013

Teaching award

I won an award for best junior teaching assistant.

2011-2013

Bachelor's in Mathematics - University of Nevada, Reno (Fall 2009 - Spring 2011)

GPA: 3.83

Competitve awards

As an undergraduate, I won first place at UNR in each of: The Putnam exam, the Intermountain Mathematics competition, and the university’s Association for Computing Machinery programming competition. My team of three won the designation of meritorious winner in the international COMAP Mathematics Competition in Modeling.

2007-2011

Clubs

I participated in a number of clubs, as well as founding UNR's math club and go club.

2007-2011