Note The job is a remote job and is open to candidates in USA. Reddit is a community-driven platform that fosters open conversations and is home to over 100,000 active communities. They are seeking a Senior Machine Learning Engineer to lead the development of machine learning models focused on GenAI Security, ensuring the safety and integrity of AI traffic and usage within the organization. Responsibilities Build and improve security-focused ML models for Reddit’s GenAI traffic, including guardrail models, semantic classifiers, anomaly detection models, and other neural network based security signals Own model development end to end define the security problem, assemble and label datasets, build ETL pipelines, engineer features, train models, evaluate quality, deploy to production, monitor performance, and retrain from production feedback Use modern deep learning architectures, including neural networks, transformers, sequence models, embeddings, and model distillation where they are the right practical fit Design rigorous evaluation suites for adversarial examples, hard negatives, long-context inputs, structured payloads, tool calls, multi-turn workflows, and real production traffic Improve model precision, recall, latency, cost, calibration, and operational reliability for high-impact production surfaces Build repeatable MLOps workflows for SPACE, including training pipelines, model lineage, artifact management, holdout evaluation, dashboards, rollback paths, and retraining loops Partner closely with ML Infrastructure, LLM Gateway, DevX, Ads, Answers, Safety, Privacy, Compliance, and other Security teams to bring security models into real production workflows Work pragmatically with Reddit’s evolving ML platform, using existing infrastructure where possible and building focused tooling when needed to keep model iteration moving Translate security goals into measurable model outcomes and help partners understand tradeoffs between risk reduction, latency, false positives, and product impact Provide technical direction to other engineers and serve as a go-to ML expert for GenAI Security and broader SPACE model needs Skills 5+ years of experience building, training, evaluating, and deploying production ML or deep learning models Hands-on experience with modern ML frameworks such as PyTorch, TensorFlow, or similar Strong practical understanding of the full ML lifecycle problem definition, data ETL, feature engineering, training, evaluation, deployment, monitoring, debugging, and retraining Experience building data pipelines and working with large-scale datasets Experience designing rigorous model evaluations, including precision/recall/F1, false positive analysis, threshold tuning, calibration, holdout sets, regression tests, and production-quality validation Experience shipping production-quality software, preferably in Python and/or Go Strong communication skills and ability to explain model behavior, risk tradeoffs, and technical decisions to cross-functional partners BS degree in Computer Science, Machine Learning, a related technical field, or equivalent practical experience Applying ML to security, privacy, trust and safety, abuse prevention, adversarial ML, or GenAI security problems Training or fine-tuning neural text models for complex inputs such as long-context prompts, structured payloads, code-like content, multi-turn interactions, or tool calls Production MLOps or model serving systems such as Airflow, Ray, MLflow, Triton, ONNX, Kubernetes, or similar Improving model quality through labeling strategy, hard-negative mining, synthetic data generation, distillation, or active learning 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 Equity in the form of restricted stock units Commission Medical, dental, and vision insurance 401(k) program with employer match Generous time off for vacation Parental leave Company Overview Reddit is the heart of the internet, where millions of people get together to talk about any topic imaginable. It was founded in 2005, and is headquartered in San Francisco, California, USA, with a workforce of 1001-5000 employees. Its website is https//www.redditinc.com. Company H1B Sponsorship Reddit, Inc. has a track record of offering H1B sponsorships, with 22 in 2026, 99 in 2025, 63 in 2024, 76 in 2023, 70 in 2022, 68 in 2021, 39 in 2020. Please note that this does not guarantee sponsorship for this specific role.