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Senior Research Engineer, LLM Training & Post-Training

London, UK💼 Full-time💰 $165,000–$165,000🗓 2026-08-12 → 2026-09-26

Core

Design, build, and optimize training and post-training pipelines for large language models to improve model quality, training efficiency, and developer productivity.

Role type

Senior Research Engineer (LLM Training & Post-Training)

Builds

Production-ready AI systems, training infrastructure, and tooling for Lightning AI's platform and customer workloads.

Domain

Artificial Intelligence / Large Language Models / Distributed Systems

Deliverable

production ML models | infrastructure

Required skills

Transformer-based LLM training and optimization, PyTorch, distributed training (multi-GPU), software engineering (Python), experiment design, model evaluation, debugging training issues

Preferred skills

SFT, RLHF, DPO, PPO, GRPO, DeepSpeed, FSDP, Megatron-LM, Hugging Face Transformers, CUDA, Triton, vLLM, SGLang, TensorRT, GPU performance optimization

Technologies

PyTorch, DeepSpeed, FSDP, Megatron-LM, Hugging Face Transformers, TRL, PEFT, Lightning Fabric, CUDA, Triton, vLLM, SGLang, TensorRT

Responsibilities

Design and optimize training/post-training pipelines; Improve model quality via fine-tuning and optimization; Build PyTorch-based training infrastructure; Optimize distributed training across multi-GPU environments; Investigate training convergence and performance bottlenecks; Design evaluation methodologies and benchmark models; Collaborate with customers to translate workloads into platform improvements; Partner with research and infrastructure teams to build production systems

Seniority

Senior, hands-on IC

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