Senior Software Engineer, Training & Experimentation in London

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. We serve solo researchers, startups, and large enterprises. Lightning AI operates globally with offices in New York City, San Francisco, Seattle, and London.

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.
• Take Ownership: We own outcomes, not just our individual work.
• Communicate Openly: We communicate directly, seek to understand, and create clarity for others.
• Build Great Teams: We lead by example, empower others, and create healthy teams.
• Raise the Bar: We're always improving ourselves.
• Think Long-Term: We design for what's next.

The Training & Experimentation team at Lightning AI builds the platform that enables developers to experiment at scale and train their own intelligence. We're looking for a Senior Software Engineer to help design and scale the backend systems that make AI development faster, more reliable, and easier to use. You'll work across distributed training infrastructure, workload orchestration, experiment management, developer tooling, and platform APIs.

This role is based in one of our San Francisco, NYC, or London office hubs, with a minimum of 2 in-office days per week and occasional team and company offsites. We are not able to provide visa sponsorship for this position at this time.

What You’ll Do:

• Design and build backend services that power AI agent orchestration and execution.
• Develop scalable APIs and platform capabilities for tool use, workflow orchestration, memory, and state management.
• Build reliable infrastructure that enables long-running, distributed AI workflows.
• Partner with product, research, and platform engineering teams to bring new agent capabilities into production.
• Improve platform reliability, observability, and performance as customer workloads continue to scale.
• Evaluate and strengthen technical architecture, engineering processes, and developer tooling.
• Maintain high standards for software quality through testing, automation, continuous delivery, and proactive management of technical debt.
• Mentor engineers on system design, distributed systems, and backend engineering best practices.

What You’ll Need:

• Extensive experience building scalable backend systems using Go, Python, Rust, or similar languages.
• Strong understanding of distributed systems, asynchronous processing, APIs, and cloud-native application architecture.
• Experience designing and operating production services at scale.
• Hands-on experience building backend platforms, developer tools, or infrastructure products.
• Familiarity with cloud platforms such as AWS, GCP, or Azure and container technologies including Docker and Kubernetes.
• Proven ability to take ownership of large technical initiatives from architecture through production.
• Commitment to software quality, automated testing, observability, and continuous delivery.
• Strong communication skills and the ability to collaborate effectively across engineering, product, research, and design teams.
• Ability to thrive in fast-moving, ambiguous environments while balancing technical excellence with product impact.

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.

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.

At Lightning AI, we are committed to fostering an inclusive and diverse workplace. We believe that diverse teams drive innovation and create better products.