Machine Learning Engineer, Answers Relevance

Reddit is hiring Senior and Staff Machine Learning Engineers for its Answers Relevance team. The role leads machine learning projects from idea to production and builds systems that improve retrieval, ranking, and AI-powered features for Reddit Answers.

Responsibilities:

• Build and improve large-scale ML systems, including retrieval and ranking, embeddings, and LLM-powered features
• Set technical direction and deliver measurable user and business impact
• Work with partner teams to shape product and technical roadmaps
• Evaluate new AI/ML approaches and support responsible LLM development
• Mentor engineers and contribute to long-term ML planning

Requirements:

• Recommendations, search, content understanding, or large-scale data and ML infrastructure
• SOTA large scale RecSys
• Foundational retriever models
• RAG systems, retrieval methods, LLM evaluation, or production LLM features
• Agentic AI, such as tool calls, MCPs, multi-agent systems, or orchestration
• Self-hosted open-weight models such as Qwen or Llama; prompt engineering, fine-tuning, post-training, or prompt optimization
• Improving grounding, instruction following, and hallucination; evaluating retrieval and generation quality
• Scaling LLM systems, including latency, caching, and cost; safety measures for prompt injection and unsafe inputs
• Defining product success metrics, feedback loops, and evaluation approaches, including human review
• 4–12 years of experience building, deploying, and operating ML systems in production
• Broad knowledge of ML fundamentals and experience applying them in production; expert-level modeling depth isn't required
• Experience developing and productionizing models with TensorFlow, PyTorch, or Hugging Face Transformers
• Experience writing production-quality code, including testing, evaluation, and monitoring; Python experience required
• Golang experience
• Experience with ML systems such as data pipelines, feature engineering, model training and serving, and production monitoring
• Strong communication and collaboration skills, and a record of delivering measurable product impact