Senior Full Stack Engineer

Senior Full Stack Engineer

Unipaas is the AI-native payments platform built for vertical software. We help platforms and marketplaces turn payments from a back-office utility into a growth lever. Our unified, fully managed service lets them deliver branded payment experiences without redirects, multiple providers, or long integration timelines. Founded in 2020 by payments-industry veterans, we serve customers across the UK, Europe, and the US in education, healthcare, and field services. Our R&D is in Tel Aviv; commercial is in London.

About the Role

We're hiring a Senior Full Stack Engineer to join the R&D team building Unipaas' core platform. You'll own product development end-to-end, on the systems that authorize, settle, and reconcile every transaction we process. This is an individual contributor role with room to grow into engineering leadership: we're looking for the engineer who will set technical direction in their domain and bring others up with them.

What You'll Do

- Architect and evolve a distributed, event-driven platform spanning multiple services and frontend surfaces, in a multi-vendor, multi-method, regulated payments context. - Own features from ambiguous problem through production and ongoing monitoring. - Use agents as a delivery norm (parallel work, automated toil, tighter feedback loops) and raise the bar for how the rest of the team uses them. - Contribute to our production agentic surface, where agent-driven flows live in front of customers, not just behind the engineering team. - Engage on architectural decisions and shape engineering practices in your area.

What We're Looking For

- 5+ years building production systems, with strong systems thinking and architectural judgment under uncertainty. - Deep proficiency in at least one modern language; comfort with TypeScript / Node.js (our stack) or the ability to ramp into it fast. We care more about how you think than which language you've shipped most. - Solid grounding in distributed systems at production scale: event-driven architectures, container orchestration, infrastructure as code, and the operational craft of running services in production (observability, debugging, incident response). - Fluency with agentic engineering tools (Claude Code, Cursor, Codex, or equivalents) as part of your day-to-day workflow. Not something you've tried, something you ship with. - High agency and a track record of technical influence: setting direction and raising the bar for engineers around you.

Nice to Have

- Experience shipping AI or agentic features into production product surfaces. - Background in fintech, payments, or marketplace platforms. - Prior team-lead or tech-lead experience.

Why Join

Competitive compensation and serious professional development. Real ownership in an early-stage company where what you ship hits production fast and matters to customers.