Senior Full Stack Engineer / Ruby on Rails / Union Square, NYC

Senior Full-Stack Engineer (Senior-Principal Level) A mission-driven startup operating at the intersection of climate and fintech is seeking a Senior Full-Stack Engineer to help build products that make sustainable building upgrades-such as heat pumps, batteries, and EV chargers-more accessible through innovative financing. This is a hybrid role based in New York City, with flexibility on level from Senior to Principal. What You'll Do Own end-to-end feature development, from ideation and architecture through deployment Write and review code across the full stack while balancing speed and quality Shape technical architecture, best practices, and decisions around technical debt and build-vs-buy Partner closely with founders and product stakeholders to influence roadmap and priorities Work cross-functionally and gain exposure to multiple areas of the business, including sales and customer discovery What You'll Bring 5+ years of experience with Ruby on Rails or similar full-stack frameworks Strong understanding of modern web application development Deep experience with database design and management Excellent communication skills and comfort working across product and technical teams Ownership mindset and ability to thrive in ambiguity Experience building systems from 0?1 and scaling them Experience or strong interest in AI, ML, and LLMs What's Offered $160,000-$200,000 base salary (NYC) plus competitive equity Health, dental, and vision coverage Unlimited PTO Opportunity to join early and make a meaningful impact at a fast-growing, mission-oriented startup in climate and fintech