Reddit, Inc.

Senior Research Engineer – Post-training, Evaluation

Reddit, Inc.

full-time

Posted on:

Location Type: Remote

Location: United States

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Salary

💰 $216,700 - $303,400 per year

Job Level

Tech Stack

About the role

  • Architect and maintain the "Reddit Benchmark" evaluation suite: A comprehensive harness that rigorously tests model capabilities across Safety, Reasoning, and Reddit-specific knowledge (slang, norms).
  • Build scalable SFT (Supervised Fine-Tuning) pipelines: Implement efficient, distributed training loops for instruction tuning, converting raw base models into helpful assistants.
  • Develop Model-as-a-Judge systems: Engineer automated evaluation pipelines using strong models (e.g., GPT-5, Nova, Claude) to grade the outputs of our internal models, enabling rapid iteration cycles.
  • Execute Synthetic Data generation strategies: Create and curate high-quality instruction sets to improve model generalization where human data is scarce.
  • Collaborate with Safety Engineering: Translate high-level safety policies into concrete evaluation metrics and unit tests that run in our CI/CD pipelines.
  • Debug post-training instability: Dive deep into loss curves and evaluation logs to identify when fine-tuning is causing alignment tax or capability degradation.

Requirements

  • 4+ years of professional experience in machine learning engineering, with a focus on LLM fine-tuning or evaluation.
  • Fluency in Python and PyTorch, with experience using libraries like Hugging Face Transformers, vLLM, or lm-eval-harness.
  • Deep understanding of Instruction Tuning (SFT) and how data quality impacts model behavior.
  • Experience building Evaluation Pipelines: You know the difference between MMLU, GSM8K, and how to build a custom domain-specific benchmark.
  • Familiarity with distributed training (FSDP/DeepSpeed) for fine-tuning jobs.
  • Strong data engineering skills for curating and cleaning instruction datasets.
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
Applicant Tracking System Keywords

Tip: use these terms in your resume and cover letter to boost ATS matches.

Hard Skills & Tools
machine learning engineeringLLM fine-tuningPythonPyTorchHugging Face TransformersvLLMlm-eval-harnessInstruction TuningEvaluation Pipelinesdata engineering