Principal Machine Learning Engineer

ZoomInfo Technologies LLC•Waltham, MA

20h•$192,500 - $302,500•Remote

About The Position

You'll build the intelligence every ZoomInfo AI agent reasons over — what's true about companies and the people in them, how they relate, and what they're buying. As a Principal Machine Learning Engineer, you will set technical direction for one or more of the hardest problems on the team: extending the B2B data graph into the long tail, resolving entity identity at scale, and reading buying intent from meaning rather than keywords. You'll own outcomes end to end, choosing classical machine learning, statistics, or language models based on what the problem calls for, not habit.

Requirements

Taken machine learning systems to production and owned them after launch, with technical leadership as an individual contributor — setting direction for a problem area, leading design review, and mentoring; depth matters more than years.
Classical machine learning expertise beyond language models, including supervised learning and feature engineering on large, messy tabular data, along with applied statistics: experiment design, statistical inference, and calibrated scores under class imbalance.
Deployed language processing at scale — text classification, information extraction, and entity linking over large volumes of multilingual, noisy text.
Built and operated LLM agents or multi-step systems in production, including tool and context design, failure analysis from traces, and evaluation for systems with no single right answer, using LLM judges validated against human labels.
Proficient in production Python and strong SQL with distributed data processing experience, and you use AI coding tools daily with rigorous review of their output.

Nice To Haves

Experience with ranking and retrieval, including embeddings, learned re-ranking, and metrics such as recall@k, MRR, and nDCG.
Propensity modeling, clustering, or entity resolution experience on messy, real-world data.
Trained and served open-weight models in PyTorch or an equivalent framework, tracking cost per unit of work.
Defended LLM systems against adversarial inputs and prompt injection, or worked on web-scale information extraction, knowledge graphs, or user memory for agents.

Responsibilities

Extend ZoomInfo's data graph into the long tail of companies with little public footprint, extracting leadership, locations, and products from company websites and detecting stale records.
Predict what the graph doesn't know yet, estimating headcount and revenue for under-documented companies using gradient-boosted trees, regression with missing inputs, and calibrated uncertainty.
Determine whether two records describe the same company or person, measuring both wrongly merged and wrongly split outcomes.
Infer buying intent from the meaning of web content across large volumes of multilingual, noisy text, feeding propensity scoring, lookalike retrieval, and contact recommendations.
Build agents that research companies and cite sources, and design the evaluations that separate a correct result from a run that merely finished.
Distill large models into smaller ones that run cost-effectively across the full dataset, owning quantization and serving as part of the same work.
Take ambiguous, high-stakes problems from undefined to shipped, setting technical direction and raising the engineering bar through design review and mentorship.