---
title: 'Senior Research Engineer, LLM Training & Post-Training at Lightning AI'
canonical: 'https://feeny.ai/job/senior-research-engineer-llm-training-post-training-lightning-ai-new-york-s4xmzg9hs6jh'
type: 'job'
last_seen: '2026-10-15'
---

# Senior Research Engineer, LLM Training & Post-Training at Lightning AI

- **Company:** Lightning AI
- **Location:** New York, NY / San Francisco, CA / Seattle, WA
- **Compensation:** $165k–$310k
- **Work type:** remote
- **Posted:** 2026-08-12
- **Last confirmed live:** 2026-10-15
- **Apply:** https://job-boards.greenhouse.io/lightningai/jobs/7860628003

## Job description

## Who We Are

Lightning AI is the company behind PyTorch Lightning. Founded in 2019, we build an end-to-end platform for developing, training, and deploying AI systems—designed to take ideas from research to production with less friction.

Through our merger with Voltage Park, a neocloud and AI Factory, Lightning AI combines developer-first software with cost-efficient, large-scale compute. Teams get the tools they need for experimentation, training, and production inference, with security, observability, and control built in.

We serve solo researchers, startups, and large enterprises. Lightning AI operates globally with offices in New York City, San Francisco, Seattle, and London, and is backed by Coatue, Index Ventures, Bain Capital Ventures, and Firstminute.

The Way We Work

The people who thrive here are builders who move fast, communicate openly, take ownership, and continuously improve themselves, their teams, and our company. Here's what that looks like in practice:

- Move with Urgency: We move quickly, make thoughtful decisions, and keep momentum. We value action over perfection and learn by shipping.
- Take Ownership: We own outcomes, not just our individual work. We make decisions that move the company forward and follow through.
- Communicate Openly: We communicate directly, seek to understand, and create clarity for others. Honest conversations help us move faster together.
- Build Great Teams: We lead by example, empower others, and create healthy teams where people can do their best work.
- Raise the Bar: We're always improving ourselves. We learn from feedback, consistently challenge ourselves to grow, and focus on the work that matters most.
- Think Long-Term: We design for what's next. We create scalable systems, simplify complexity, and use AI and automation to amplify our impact.

## What We're Looking For

We're are looking for an experienced Senior Research Engineer who has built, trained, and optimized modern transformer-based language models to join our Research Engineering function at Lightning.

This role will focus on advancing how large language models are trained, fine-tuned, evaluated, and deployed across Lightning AI's platform and real-world customer workloads. It will work across model training, post-training, PyTorch, distributed systems, and AI systems engineering to improve model quality, training efficiency, and developer productivity while collaborating closely with researchers, infrastructure engineers, and customers.

We're looking for someone who enjoys turning cutting-edge research into production systems. You have deep experience training and improving transformer-based language models, strong software engineering fundamentals, and a passion for solving difficult problems across model training, evaluation, and AI systems. Rather than building applications on top of existing models, you're motivated by improving the models themselves and the systems that power them. Our work spans models that power the Lightning AI platform, customer-specific model workloads, and research that translates into reusable training and platform capabilities.

This role is hybrid with a minimum of 2 in-office days per week in San Francisco, Seattle, NYC, or London, with fully remote work considered for candidates outside of our office hub locations. All employees participate in occasional team and company offsites.

## What You'll Do

- Design, build, and optimize training and post-training pipelines for large language models.
- Improve model quality through supervised fine-tuning, continued pretraining, preference optimization, reinforcement learning, evaluation, and experimentation.
- Build and improve PyTorch-based training infrastructure, tooling, and developer workflows.
- Optimize distributed training across multi-GPU environments by improving throughput, memory efficiency, scalability, and GPU utilization.
- Investigate model training issues, including convergence, instability, communication overhead, and performance bottlenecks.
- Design evaluation methodologies, benchmark models, analyze failure modes, and acheive model improvements through experimentation.
- Collaborate directly with customers to understand real-world workloads and translate those learnings into improvements across Lightning AI's research platform.
- Partner closely with research, infrastructure, and platform engineering teams to build production-ready AI systems.
- Contribute to open-source projects through new features, tooling improvements, documentation, and community engagement

## What You’ll Need

Required Qualifications

- Significant experience training, fine-tuning, evaluating, and/or optimizing transformer-based language models using PyTorch.
- Experience with modern LLM training and post-training techniques such as continued pretraining, SFT, RLHF, preference optimization (DPO, PPO, GRPO), reward modeling, or similar approaches.
- Strong understanding of distributed training and multi-node systems, with experience improving training performance, scalability, and/or efficiency.
- Strong software engineering fundamentals, including building production-quality Python software and research tooling.
- Experience designing experiments, evaluating model performance, and debugging complex training and/or optimization issues.
- Excellent communication and collaboration skills, including the ability to work effectively across research, product, infrastructure, and customer-facing engagements.
- Comfortable working in fast-moving, ambiguous environments where priorities evolve over time.
- Master's degree, PhD, or equivalent industry experience in Machine Learning, AI, Computer Science, or a related field

Ideal Experience

Experience with one or more of the following:

- DeepSpeed, FSDP, Megatron-LM, Hugging Face Transformers, TRL, PEFT, Lightning Fabric, NVIDIA Molt, or similar training frameworks.
- CUDA, Triton, vLLM, SGLang, TensorRT, or other AI systems and performance optimization technologies.
- GPU performance optimization, mixed precision, memory optimization, or distributed training optimization.
- Open-source contributions, research publications, or production AI platforms supporting large-scale training or inference workloads.
- Startup experience or experience working on highly cross-functional engineering teams.

## Compensation

We are committed to offering competitive compensation that reflects the value each team member brings to our mission. Final offers are based on factors such as experience, skills, geographic location, and role expectations. In addition to base salary, our total rewards package for eligible roles includes a discretionary bonus, a meaningful equity component, and comprehensive benefits.

The anticipated annual base salary range for this role is: $165,000—$310,000 USD

## Benefits and Perks

We offer a comprehensive and competitive benefits package designed to support our employees’ health, well-being, and long-term success:

- Comprehensive Health Coverage: Medical, dental, and vision coverage for employees and eligible dependents.
- Meaningful Equity: RSUs that give employees a stake in the company's long-term success.
- Retirement Savings: 401(k) matching (U.S.) and pension contributions (U.K.).
- Flexible Time Off: Unlimited PTO, company holidays, and floating holidays to support work-life balance.
- Company-Wide Winter Break: Two weeks of company closure each winter to disconnect and recharge.
- Paid Parental & Family Leave: Paid leave to support you and your family through life's important moments.
- Professional Development: Annual learning and development allowance to support your professional growth.
- Wellness Benefits: Wellness and work-from-home stipends to support your physical and mental well-being.
- Sabbatical Program: Four weeks of paid sabbatical leave after four years of service.
- Flexible Work: Flexible schedules and a hybrid work model for our office-based teams.
- In-Office Meals: Complimentary meals at our office hubs.

Benefits may vary by location, team, and role.

At Lightning AI, we are committed to fostering an inclusive and diverse workplace. We believe that diverse teams drive innovation and create better products. We provide equal employment opportunities to all employees and applicants without regard to race, color, religion, gender, sexual orientation, gender identity, national origin, age, disability, veteran status, or any other protected characteristic. We are dedicated to building a culture where everyone can thrive and contribute to their fullest potential.

## About Lightning AI

## Company Overview
- **One-liner**: Lightning AI provides an end-to-end cloud platform for building, training, and deploying AI models and applications, combining developer-first software with large-scale GPU infrastructure.
- **Entity Type**: Private (Series unknown; merged with Voltage Park in January 2026)
- **Headquarters**: New York, New York, USA
- **Founded**: 2019
- **Founders**: Will Falcon (CEO)

## Core Business
- **Primary industry**: Cloud AI platform, AI infrastructure, AI developer tools
- **Target customers**: B2B (developers, startups, and large enterprises); also serves individual developers (B2C for open-source community)
- **Mission or purpose**: Empower anyone to build AI.

## Products & Services
- **[PyTorch Lightning]**: Open-source deep learning framework used by over 5 million developers; simplifies training and fine-tuning models.
- **[Lightning AI Cloud Platform]**: SaaS platform for end-to-end AI development – including GPU access, model training, deployment, inference, team management, and observability.
- **[GPU Infrastructure]**: Fleet of 35,000+ owned and operated H100, B200, and GB300 GPUs, available on-demand with burst capacity.

## Market Standing
- **Valuation/Market Cap**: Not disclosed
- **Key Metric**: Annual Recurring Revenue (ARR) grew from $18M to over $500M following the merger with Voltage Park (January 2026).
- **Notable Investors/Partners**: Backed by Coatue, Index Ventures, Bain Capital Ventures, and Firstminute.
- **Growth Signals**: Completed merger with Voltage Park in January 2026, creating the first “AI cloud”; platform used by 400,000+ developers; 200 employees globally; offices in NYC, San Francisco, Seattle, and London.

## Competitive Advantages
- Only platform that bundles AI software with neocloud-priced GPU infrastructure in a single, unified experience – a category they created.
- Deep open-source roots (PyTorch Lightning) give them strong developer trust and community (5M+ users).
- Massive owned GPU fleet (35,000+ accelerators) with ability to burst across multiple clouds.
- “Software-first and infrastructure-native” approach reduces complexity for AI teams.

## Strategic Focus
- Continue to scale as the “first cloud built for AI,” eliminating the need for customers to stitch together separate tools or negotiate with dozens of GPU vendors.
- Expand GPU marketplace partnerships with major cloud providers and neoclouds.
- Grow enterprise adoption by offering enterprise-grade reliability and security without the overhead of hyperscaler complexity.

## Why Work Here
- **Culture**: Hybrid work model (2 days/week in-office); offices in NYC, SF, Seattle, London with flexible schedules.
- **Notable benefits**: Competitive compensation (RSUs), 401(k) matching, paid parental/family leave, four-week sabbatical after four years, two-week company-wide winter break, wellness benefits, professional development stipend, in-office meals, and home-office stipend for remote employees.
- **Engineering culture**: Emphasis on craftsmanship, simplicity, speed, and principled execution. Encourages contributions to open source. “Move fast with precision” – focus on completing one goal at a time.
- **Growth opportunity**: Own transformative projects in a fast-growing company (ARR jumped from $18M to $500M+). Global team of 200 with a strong mission.

## Sources
1. [lightning.ai/careers](https://lightning.ai/careers)
2. [job-boards.greenhouse.io/lightningai](https://job-boards.greenhouse.io/lightningai)
3. [businesswire.com](https://www.businesswire.com/news/home/20260121371691/en/Lightning-AI-and-Voltage-Park-Complete-Merger-to-Create-the-First-Cloud-Built-for-AI)
4. [linkedin.com/company/pytorch-lightning](https://www.linkedin.com/company/pytorch-lightning)
5. [builtinnyc.com/company/lightning-ai](https://www.builtinnyc.com/company/lightning-ai)

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