Senior Software Engineer, RLE
About HandshakeHandshake was founded on a simple belief that everyone deserves a path to a great career, regardless of where they went to school or who they know. Today, we power 25 million job seekers, 1 million+ employers, and 1,600 educational institutions.In 2025, we started Handshake AI and built the fastest-growing AI data business in history. We work directly with frontier AI lab researchers to create evaluations, publish benchmarks, and push the boundary of data. We’ve grown from $0 to ~$1B run rate and pay ~$60M to over 30K individuals every month.Why Join Handshake NowShape how every career evolves in the AI economy, at global scale, with impact your friends, family and peers can see and feelPartner hand-in-hand with world-class AI labs, Fortune 500 partners and the world’s top educational institutionsWork together with engineers, scientists, operators, and more from Palantir, Meta, Scale AI, and former YC foundersBuild a massive, fast-growing business with billions in revenueAbout Handshake AIHuman data is the core infrastructure to AI advancement. Frontier AI labs currently improve model capabilities with various data-intensive post-training techniques. We believe that data spend for AI training will increase by 3-5x in the next few years and continue for much longer as models take on new domains. Handshake AI supports all of the frontier AI labs, working on their most complex data at the largest scale.About The RoleWe’re hiring a Senior Software Engineer to build our Reinforcement Learning Environments (RLE) platform—the interactive systems where frontier AI models learn to complete real-world work.RLE environments simulate workflows (e.g., software engineering, finance, legal) with realistic tools, constraints, and feedback loops. The data generated powers training and evaluation for model quality, robustness, and task completion.This is a high-ownership role with direct impact on how models learn and how quickly new domains scale.What You’ll DoBuild and scale our reinforcement learning environments and the platforms behind themDrive architecture for scalable, reliable, extensible environment systems and data generation pipelinesPartner with Research, Product, and Ops to turn ambiguous needs into production systemsBuild modular, plug-and-play domains that integrate cleanly with training and evaluation loopsRaise the bar on reliability, observability, performance, and data qualityWhat We’re Looking For6+ years building backend, distributed systems, or ML infrastructureProficiency with ReactJS and TypeScript, with deep knowledge of backend architectures.Strong command of relational databases (e.g., PostgreSQL), data modeling, system design, and distributed systems principles.Experience with cloud infrastructure (AWS, GCP), CI/CD pipelines, and operating production systems at scale.Nice to HaveExperience with RL training infrastructure, simulation systems, or evaluation platformsWorking in an operations-heavy, tech-enabled environmentExperience supporting applied ML or AI research teamsWhat Success Looks LikeRLE becomes a trusted platform for training workflow-capable modelsNew domains launch quickly with high-quality dataSystems are reliable, scalable, and drive measurable model improvementsPerksHandshake delivers benefits that help you feel supported—and thrive at work and in life.The below benefits are for full-time US employees.🎯 Ownership: Equity in a fast-growing company💰 Financial Wellness: 401(k) match, competitive compensation, financial coaching🍼 Family Support: Paid parental leave, fertility benefits, parental coaching💝 Wellbeing: Medical, dental, and vision, mental health support, $500 wellness stipend📚 Growth: $2,000 learning stipend, ongoing development💻 Office: Commuting support, free lunch, and gym in our SF office🏝 Time Off: Flexible PTO, 15 holidays + 2 flex days🤝 Connection: Team outings & referral bonusesCompensation Range: $225K - $250K