Staff Machine Learning Engineer, AI Security

Details

Reddit's AI Security team within the Security Platform Engineering organization builds security into Reddit's products, engineering systems, AI platforms, and operational infrastructure. The team develops machine learning systems that detect and prevent risks such as prompt injection, jailbreaks, sensitive data exposure, and unsafe or unauthorized AI behavior, building on Reddit's centralized LLM Guardrails Platform.

This is a strategic and hands-on individual contributor role focused on leading the development, training, and optimization of models for AI security at Reddit. The role includes ownership of model architecture, training data, experimentation, and technical leadership across teams.

Responsibilities

• Select, adapt, fine-tune, evaluate, and deploy pretrained models and lightweight classifiers for Reddit-specific security problems.
• Build reproducible training and evaluation pipelines on Reddit's ML platform.
• Partner with platform engineers to improve inference performance, resource efficiency, and operational reliability.
• Set the technical vision and multi-quarter modeling roadmap.
• Partner with cross-functional teams to gather requirements, define model architectures, and iterate on model development.
• Conduct model evaluations and performance analysis to improve accuracy and adversarial robustness.
• Define launch criteria that balance false positives, latency, throughput, reliability, and cost.
• Own training-data quality and the production model lifecycle, using monitoring, incident findings, and red-team feedback to guide dataset improvements, retraining, and safe rollout or rollback.
• Establish best practices for responsible ML development and deployment, including reproducible experiments, testing, model and data lineage, and privacy-aware data use.
• Stay current with research in NLP, large language models, and relevant multimodal techniques, translating promising advances into measurable model improvements.
• Mentor engineers and lead technical discussions and reviews, shaping the team's long-term ML capabilities and AI security direction.

Requirements

• 8+ years of experience developing machine learning models, with substantial hands-on model training experience, demonstrated production impact, and a record of leading complex initiatives across teams.
• Strong background in Python programming, software engineering, and deep learning frameworks and libraries such as TensorFlow, PyTorch, or Hugging Face Transformers.
• Deep understanding of neural network architectures and optimization.
• Proficiency in data preprocessing, tokenization, embeddings, language modeling, and model calibration.
• Expertise in scalable data pipelines and distributed training frameworks such as Ray Train or PyTorch Distributed.
• Strong understanding of hardware and system tradeoffs.
• Demonstrated rigor in experimental design and model evaluation, including representative holdouts, ablation studies, adversarial tests, and error analysis to diagnose training issues, bias, and generalization gaps.
• Excellent written and verbal communication skills, with the ability to explain model behavior, security risk, uncertainty, and tradeoffs to technical and non-technical partners.

Preferred Qualifications

• Experience applying ML to security, trust and safety, fraud, privacy, or related adversarial domains.
• Experience with adversarial training, model distillation, active learning, or synthetic-data generation to improve model quality, robustness, and training efficiency.

Benefits

• Comprehensive healthcare benefits and income replacement programs.
• 401(k) with employer match.
• Global benefit programs covering workspace, professional development, caregiving support, and other needs.
• Family planning support.
• Gender-affirming care.
• Mental health and coaching benefits.
• Flexible vacation and paid volunteer time off.
• Generous paid parental leave.

Compensation

The base salary range for this position is $230,000–$322,000 USD. The position is also eligible to receive equity in the form of restricted stock units and, depending on the position offered, may be eligible to receive a commission.