Senior Full Stack Developer

About Delta Labs Delta Labs uses AI to simulate and predict consumer behaviour at scale. We build Elaiia, a simulation engine that generates AI Twins — intelligent synthetic agents that mirror real consumer populations. Our clients use Elaiia to simulate customer decisions before committing to them: pricing strategies, product launches, campaign messaging, channel allocation. We replace surveys, focus groups, and intuition with simulation-based evidence. We're a small, focused team and we intend to stay that way. We give people ownership, trust, and the autonomy to do their best work. We work with urgency and intellectual honesty and expect new team members to match our pace. We seek individuals who are curious, rigorous, and want their work to have demonstrable impact. If you're drawn to the idea of a small team building something that hasn't existed before, let's build together. About The Role As a Full Stack Developer at Delta Labs, you will design and build the systems that power Elaiia's simulation platform. The Engineering team owns the full stack, from database schema to production UI, and is responsible for making Elaiia fast, reliable, and scalable. THE STACK A modern TypeScript frontend stack built on Next.js and React, backed by PostgreSQL and a set of Python microservices. Long-running study workflows are orchestrated as durable background jobs. OpenAI, Anthropic and Google Gemini are deeply integrated into the product layer, with LangGraph agents and full LLM tracing and evals. Deployed on Vercel and Microsoft Azure. Responsibilities Design and build production features across the full stack, from data model to UI Integrate LLM APIs into production workflows: prompt pipelines, structured outputs, token optimization, and reliability at scale Build and operate long-running, multi-step simulation workflows — durable jobs that run for minutes or hours and cannot silently fail Treat LLM quality as measurable: tracing, evals, and regression checks on the AI paths you own Own entire features end-to-end and take responsibility for their performance, quality, and correctness Collaborate with the research team to transition experimental AI capabilities — statistical persona models, agent architectures — into production-grade systems Improve and extend the platform architecture as simulation workloads grow in complexity and volume Ship continuously to maintain the pace the company needs YOU MAY BE A FIT IF You have 4+ years of experience shipping production web applications in TypeScript You are strong in the modern React/Next.js ecosystem, and care about code quality, performance, and maintainability You are comfortable reading and writing Python, or ready to be — a meaningful part of our backend is Python services You have designed relational database schemas that hold up under real-world scale and complexity You have worked with or are deeply curious about LLM integration — prompt engineering, structured outputs, retrieval-augmented generation, agent architectures You use AI tools as a core part of your development workflow and consider AI-assisted engineering the standard, not optional You are comfortable working with ambiguity and incomplete specifications You communicate clearly about technical trade-offs and write useful documentation STRONG CANDIDATES MAY ALSO Have built AI-powered features used by real customers in production Have shipped LLM features with real evaluation and observability behind them, not just prompts that looked good in review Have built asynchronous, long-running job pipelines and know how they fail Have worked on multi-tenant including enterprise SSO Have worked across both Vercel and cloud infrastructure like Azure Have worked in a high-velocity early-stage environment LOCATION This role is based in Switzerland. We work from Zürich and meet regularly in person. Candidates should be based in Switzerland or open to relocation. Benefits We offer a competitive salary, potential equity participation, and the opportunity to build a company from its earliest stages. Delta Labs is an equal opportunity employer. We welcome applications from all backgrounds