Backend / AI Systems Engineer

Spellbook is the most comprehensive AI copilot for transactional lawyers. It works directly inside Microsoft Word to help legal teams draft, review, and negotiate contracts up to 10x faster and with greater precision. Today, more than 4,000 law firms, in-house teams, and solo practitioners rely on Spellbook to simplify their workflows and eliminate the drudgery of everyday contract work.

We are backed by leading investors including Khosla Ventures, Thomson Reuters Ventures, Inovia Capital, The LegalTech Fund, Bling Capital, and Moxxie Ventures. The company recently raised $50 million in Series B funding, led by Keith Rabois at Khosla Ventures, bringing its total funding to more than $80 million.

*This is an existing vacancy

THE ROLE (BACKEND / AI SYSTEMS ENGINEER)

You’ll build the backend systems that power Spellbook’s product experiences, including both traditional software services and AI-driven workflows. This is a hands-on, high-ownership role for an engineer who cares about product outcomes and understands what requires scale vs what does not, and can turn ambiguity into robust systems that lawyers trust.

THE TECH STACK

Node.js, TypeScript, Express, tRPC, MongoDB, Docker, AWS, CDK, LLM providers (OpenAI, Anthropic, and others)

RESPONSIBILITIES

- Build and scale backend systems that support core product functionality across Spellbook (Reviews, Chat, Library, and more).

- Design low-latency, high-reliability search, inference, and orchestration layers for AI features

- Build and operate RAG retrieval at scale with production-grade performance optimization and permissions-correct data isolation.

- Own core platform concerns for AI: rate limiting, retries, consistency, fallbacks, safe degradation

- Partner closely with Product and Design to make good tradeoffs between latency, accuracy, UX, and reliability.

- Use modern development workflows, including agent-assisted coding, to accelerate delivery while maintaining rigorous review, testin...