[Remote] Senior Machine Learning Engineer, GenAI Security

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.ResponsibilitiesBuild 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 signalsOwn 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 feedbackUse modern deep learning architectures, including neural networks, transformers, sequence models, embeddings, and model distillation where they are the right practical fitDesign rigorous evaluation suites for adversarial examples, hard negatives, long-context inputs, structured payloads, tool calls, multi-turn workflows, and real production trafficImprove model precision, recall, latency, cost, calibration, and operational reliability for high-impact production surfacesBuild repeatable MLOps workflows for SPACE, including training pipelines, model lineage, artifact management, holdout evaluation, dashboards, rollback paths, and retraining loopsPartner closely with ML Infrastructure, LLM Gateway, DevX, Ads, Answers, Safety, Privacy, Compliance, and other Security teams to bring security models into real production workflowsWork pragmatically with Reddit’s evolving ML platform, using existing infrastructure where possible and building focused tooling when needed to keep model iteration movingTranslate security goals into measurable model outcomes and help partners understand tradeoffs between risk reduction, latency, false positives, and product impactProvide technical direction to other engineers and serve as a go-to ML expert for GenAI Security and broader SPACE model needsSkills5+ years of experience building, training, evaluating, and deploying production ML or deep learning modelsHands-on experience with modern ML frameworks such as PyTorch, TensorFlow, or similarStrong practical understanding of the full ML lifecycle: problem definition, data ETL, feature engineering, training, evaluation, deployment, monitoring, debugging, and retrainingExperience building data pipelines and working with large-scale datasetsExperience designing rigorous model evaluations, including precision/recall/F1, false positive analysis, threshold tuning, calibration, holdout sets, regression tests, and production-quality validationExperience shipping production-quality software, preferably in Python and/or GoStrong communication skills and ability to explain model behavior, risk tradeoffs, and technical decisions to cross-functional partnersBS degree in Computer Science, Machine Learning, a related technical field, or equivalent practical experienceApplying ML to security, privacy, trust and safety, abuse prevention, adversarial ML, or GenAI security problemsTraining or fine-tuning neural text models for complex inputs such as long-context prompts, structured payloads, code-like content, multi-turn interactions, or tool callsProduction MLOps or model serving systems such as Airflow, Ray, MLflow, Triton, ONNX, Kubernetes, or similarImproving model quality through labeling strategy, hard-negative mining, synthetic data generation, distillation, or active learningBenefitsComprehensive Healthcare Benefits and Income Replacement Programs401k with Employer MatchGlobal Benefit programs that fit your lifestyle, from workspace to professional development to caregiving supportFamily Planning SupportGender-Affirming CareMental Health & Coaching BenefitsFlexible Vacation & Paid Volunteer Time OffGenerous Paid Parental LeaveEquity in the form of restricted stock unitsCommissionMedical, dental, and vision insurance401(k) program with employer matchGenerous time off for vacationParental leaveCompany OverviewReddit 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 SponsorshipReddit, 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.