Founding Backend Engineer

About the Role

LedgerUp is looking for a founding backend engineer who’s hungry to build, ship, and scale real products—not just models or prototypes. You’ll work directly with the founders to architect the systems behind Ari, our AI billing teammate, and the platform that powers automated billing, collections, and revenue intelligence for fast-growing B2B companies.

This is not a narrow backend role. You’ll own features end to end—from customer interviews to API design, infra decisions, modeling workflows around LLMs, and production deployment. You’ll work across our entire system as we scale, help define our technical roadmap, and shape the engineering culture from day one.

If you love fast-paced environments, want massive ownership, and enjoy the challenge of building deeply reliable systems around LLMs, this role is for you.

What You’ll Do

• Design, build, and scale backend systems that power our AI agent and automate complex financial workflows
• Develop LLM-powered features, including retrieval pipelines, reasoning systems, structured output, and agentic workflows
• Own features end-to-end: customer discovery, architecture, implementation, rollout, and iteration
• Create and refine APIs that sync with Stripe, Salesforce, QuickBooks, HubSpot, and other financial/CRM systems
• Evaluate and evolve our AI and data tooling as we scale usage and reliability expectations
• Participate in roadmap planning, identify technical leverage points, and influence core product decisions
• Meet with customers to gather feedback and deeply understand their operational pain points
• Build resilient, high-throughput systems—event-driven pipelines, CDC, billing workflows, and complex contract logic
• Ensure accuracy and reliability in mission-critical financial operations where details matter

Who You Are

• Backend-focused engineer with strong experience building production systems
• Hands-on LLM experience (prompting, fine-tuning, agents, retrieval, or model integration at scale)
• Thrives in fast-paced, zero-to-one environments—you move quickly and don’t need heavy direction
• Bias toward ownership: you love being responsible for outcomes, not just tasks
• Comfortable working across the stack when needed (infra, integrations, data modeling)
• Obsessed with correctness and reliability in complex systems
• Strong communicator who can talk to customers, founders, sales, and finance teams
• Excited to help define culture, process, and engineering standards from scratch
• Wants to be in-office with a tight, high-velocity team (we are onsite in Downtown SF 5 days per week)