Staff Sofware Engineer (Backend Systems) in Cambridge

Lightfield is looking for a Staff Engineer to be one of the most senior technical contributors on the engineering team, driving the architecture and execution of the backend systems that power our core product. Since emerging from private beta, Lightfield has seen rapid adoption - hundreds of businesses signing up each week, including larger teams relying on the product in production-critical workflows.

The product surface area is expanding quickly: we’re building an external API platform, shipping new AI-driven capabilities, and designing the data model and system architecture to support increasingly complex customer workflows. You’ll work primarily in a Postgres-backed, multi-tenant backend (Node/TypeScript on AWS) where API design and data architecture directly shape the product experience.

• Lead the architecture and execution of Lightfield’s most critical backend work streams - API platform, core data model, and systems that underpin new product capabilities.
• Scale our API platform: multi-tenant isolation, versioning, rate limits/quotas, idempotency, and measurable latency/throughput goals.
• Partner with co-founders and product leadership to translate product direction into backend architecture decisions.
• Explore and ship agentic capabilities that require safe sandbox code execution (isolation, resource limits, auditability, security guardrails).
• Design and ship customer-defined CRM schema (custom fields, custom objects, flexible relationships) without sacrificing query performance or clean APIs.
• Lead complex projects end-to-end - for example, taking custom objects from data model → migrations → query patterns → API ergonomics.
• Own the abstractions that the broader engineering team builds on top of.
• Raise the bar through design leadership, code review, and technical mentorship.
• Contribute to hiring as the team grows - helping identify and close strong technical talent.

Most backend roles at this stage are about keeping things running. This one is about shaping what gets built. Lightfield’s product ambitions are outpacing the current team’s capacity to design and execute the backend systems behind them - the API platform, the data architecture, the systems that power new AI-driven capabilities. This is a chance to be one of the most influential engineers at a company with genuine traction, a strong team, and hard problems that are driven by product growth rather than technical debt. Your judgment will shape the product, not just the infrastructure.

Benefits:

• Meaningful early equity.
• Health insurance (medical, dental, vision).
• 3 weeks of PTO.
• 11 paid company holidays + we enjoy a winter holiday break.
• Wednesdays work from home.
• Regular team dinners, events, offsites, and retreats.
• 3 months of paid family leave.
• 401k plan.
• Other perks include: commuter and lunch stipend.

Qualifications:

• You’ve designed and shipped APIs or platform-level systems that other engineers and external customers build on (versioning, auth, rate limits, backward compatibility).
• 8+ years of experience building and scaling backend systems, with meaningful time spent in technical leadership roles (tech lead, staff engineer, or equivalent).
• Comfortable in a fast-moving, early-stage environment where the team is small, the scope is large, and you’re expected to operate with significant autonomy.
• You’ve owned the architecture of significant product-facing systems - not just infrastructure, but the backend that drives what customers experience.
• You’ve built for multi-tenant SaaS at scale and understand isolation, data growth, and performance tradeoffs.
• You make the engineers around you better through the quality of your technical judgment and your willingness to engage deeply in design and code review.
• You’ve led large, ambiguous projects end-to-end - defined the approach, sequenced the work across multiple engineers, and driven execution through to delivery.
• You have strong product instincts - you care about why something is being built, not just how, and you prioritise based on customer impact.
• Strong experience with relational databases (Postgres preferred) - you understand query optimization, indexing strategy, and the tradeoffs involved in scaling a database-backed application.