Senior Full Stack Engineer (Fast growing startup)

Join Stairpay, a fast-growing startup revolutionizing the affordable housing sector. As a Senior Full Stack Engineer, you'll have the opportunity to shape the future of real estate technology. You'll work on a cutting-edge platform that manages the entire purchasing journey, utilizes AI for document ingestion and regulatory checks, and provides residents with an app to manage their homes. You'll have the autonomy to make architectural decisions, work directly with clients, and set the technical direction of the company. Enjoy a range of benefits, including generous stock options, remote work flexibility, and a gym in the office.

Missions

• Concevoir, architecturer, mettre en œuvre, déployer et itérer sur des systèmes complets, en prenant des décisions architecturales autonomes.
• Diriger et orchestrer les agents à travers la mise en œuvre, la révision et la vérification, en apportant les fondamentaux à ce qui revient.
• Travailler directement avec les clients, participer aux appels avec les associations de logement, valider les solutions avec de vrais utilisateurs.

Profil recherché

• AI raises the floor. We raise the ceiling - that's our engineering vision. The floor is everything that happens without a person doing it by hand: implementing, verifying, reviewing, deploying, correcting, rolling back, around the clock. The ceiling is what's possible, and raising it is our responsibility
• You'd be the overarching orchestrator - you set direction, wield the tooling exceptionally well, and own the result. You'll shape what the harness looks like and drive change classes up the ladder, while shipping product to housing associations who are using this every day
• Senior full-stack, production-hardened - years of shipping complete systems across frontend, backend and database, and operating them once they're live. You've been on the hook when it broke
• Architectural judgement - you make structural decisions autonomously and can defend them: service boundaries, data modelling, where complexity belongs and where it absolutely doesn't
• Deep TypeScript, React and Next.js - advanced patterns, rendering strategies, state management; you have opinions and reasons for them
• Databases you'd trust with money - schema design, query optimisation, migrations, integrity constraints, history. You think in invariants, not just tables
• Cloud and infrastructure - AWS in production, comfortable with infrastructure as code (we use Pulumi), environments, secrets and blast radius
• You direct AI at a high level and catch what it gets subtly wrong - this is a core assessed skill, not a bonus. We want to hear where you've overridden a model and why you were right to. You don't need to have built agent infrastructure before; you need the engineering judgement to build it and the appetite to learn fast
• You want to invent how we build, not just what we build - the AI infrastructure this company runs on is still being designed, and there's no playbook to copy. We want someone who'd rather design it than inherit it
• Domain correctness is non-negotiable to you - in fintech, plausible-looking maths that's wrong is worse than no feature. You test the money paths like someone will audit them, because someone will
• Product-first - you argue about what to build and for whom before you argue about how. We hire engineers who are product people first, deliberately

Nice to have:

• Accountable - utterly accountable, and driven by results. You'll be joining a small team who are keenly motivated to improve our systems and our output every day
• Verification discipline - meaningful tests, contracts, data invariants, evals, observability. You understand that when code becomes cheap to produce, the definition of "correct" becomes the durable asset - and you'd enjoy being one of the people who builds ours
• Raising others - you review well, mentor without taking over, and leave the codebase easier for the next person and the next agent
• Prioritisation under pressure - you can tell a fire from a smoke alarm and say no to the wrong work
• Client-facing - comfortable on calls with housing associations, translating their workflows into system design and technical decisions back into plain English
• Fintech, proptech or regulated-domain experience - genuinely useful here, though the domain is learnable and the judgement isn't