Founding Engineer [AI Fintech]

About Us

Rainbow is building the next generation of treasury operations — designed for global mid-market and enterprise finance teams.

We’re a team of AI engineers and finance operators who have spent years inside financial operations, and we’re using that experience to build the system that modern companies now require.

Rainbow is backed by Bessemer Venture Partners, Vertex, Hanaco, and leading serial entrepreneurs.

We’re now expanding the team to meet growing demand — and shaping the future of how companies run their finance operations.

The Role

Join Rainbow as a Founding Engineer working across customers and product. You’ll go deep into real treasury workflows, solve them hands-on, and translate those learnings into scalable product and architecture with the core engineering team.

We’re looking for a product-minded builder — someone who likes to get close to the problem, craft working software end-to-end, and turn complexity into elegant systems. You’ll iterate fast, build with users, and help shape the product and engineering culture from day one.

What You’ll Do

• Design and build AI-powered treasury automation systems from scratch
• Work directly with enterprise customers to understand workflows and implement solutions
• Develop APIs, data pipelines, and automation services that handle critical financial operations
• Lead technical decisions across the stack (backend, data, AI/ML, cloud)
• Own complex projects from concept to production, with autonomy and accountability
• Contribute to product UX and be comfortable jumping into frontend when needed

We’re Looking For Someone Who

• Has a strong track record of end-to-end product development and a builder mindset
• Is experienced with modern backend development — Python/TypeScript/Java/Golang
• Is comfortable contributing to the frontend when needed (React/TypeScript a plus)
• Is familiar with cloud-native development, APIs, and modern infrastructure
• Has experience with AI/ML systems, LLMs, or automation workflows
• Thrives in customer-facing environments and enjoys turning needs into product
• Takes ownership, moves fast, and can navigate complexity and ambiguity

Bonus: Experience building AI agents in production, or financial/enterprise software.

This isn’t a role for someone who only wants to sit behind a keyboard. It’s for someone who wants to live in the problem space, work with customers, and use those insights to build a category-defining product.