Founding Engineer (Fintech) @ Rainbow

About Us

The pain is universal: finance teams stitch together spreadsheets and dashboards just to answer basic questions about their cash flow. They feel constantly behind, reactive instead of in control. By the time their systems tell them what happened, it's too late to optimize.

This is bad for operators managing treasury today, directly hits the bottom line—costs companies millions in lost yield and higher borrowing costs. But it's wide open for AI-native contenders.

Rainbow is building an AI-powered treasury system of action for global companies that turns forecasts into execution with the intelligence and reliability that modern finance demands. We're backed by Bessemer Venture Partners, Vertex Ventures, Hanaco Ventures, and leading angels in fintech. We work with companies from private mid-market to public enterprises.

The Inevitable Future: Every company becomes financially intelligent. We're building the foundations for that transformation now.

The Role

Join Rainbow as a founding engineer who works both with customers and on the product. You'll alternate between being embedded with customer teams to understand their needs and working with our core engineering team to advance the platform.

We’re looking for a product-minded engineer who loves to build. Someone who’s comfortable starting with hands-on solutions alongside customers, and then turning those learnings into scalable product and architecture. This role is about crafting real, working software — iterating quickly and transforming complex, real-world workflows into reliable systems. If you take pride in bringing ideas to life end-to-end, this role offers the opportunity to create meaningful impact and shape a product from the ground up.

What You'll Do:

• Design and build AI-powered treasury automation systems from scratch
• Work directly with enterprise customers to understand their workflows and implement solutions
• Develop APIs, data pipelines, and AI models that handle critical financial operations
• Lead technical decisions across our full stack (backend, AI/ML, data infrastructure)
• Take ownership of complex projects from concept to production deployment

We Need Someone Who:

• Has a strong record of end-to-end product development and builder's hunger
• Is comfortable with modern development practices (Python, cloud infrastructure, APIs)
• Has experience with AI/ML systems, LLMs, or automation workflows
• Can work directly with customers in enterprise environments
• Takes high ownership and can push through complex technical challenges

Bonus: Experience building AI agents in production

This isn't just writing code—it's living in the problem space, serving customers directly, and using those insights to build a better product.