Senior Backend Developer

Payroll that runs itself. You build the part that runs it. quinn is an app-based managed payroll and employment-administration service for households and companies who employ people directly. The customer stays the legal employer. quinn registers the employment, runs payroll, pays salaries, social insurance and taxes, and handles every filing that follows, on their behalf and automated end to end. We don’t sell payroll software. We run payroll. We operate in Switzerland, Germany and the UK. Last year more than CHF 200 million in salaries ran through our systems, correct to the cent. The purpose behind it is simple: fair employment, for all. Why this role exists Every market brings its own authorities, insurers, pension funds and tax rules. Our answer is quinn ONE: one platform for every product and market, with a shared core for what all countries have in common and a configuration layer per country on top, designed to carry twelve countries. The backend is that core. It is a modular monolith in C#, .NET 10 and PostgreSQL, serving one quinn app for employers, employees and our own support team, Maestro for batch processing, and our AI agents. Development has started, and the foundations the platform will run on for years are being laid now. This role is fully focused on quinn ONE. Our existing products are not part of it. What you will own • Backend modules, end to end. Design, build, test and run modules and the APIs they expose, from requirements to production, without waiting to be handed a ticket. • The data. The PostgreSQL model the platform rests on: schema design, migrations, transactions, indexing, and the calculations that must be right to the cent. • The foundations. Audit trail, logging, versioning of our APIs and services, and the database upgrades that keep the platform current. • Reliability and security in production. Tests, observability, performance, and data protection by design: an API returns what is needed, not everything that is available. Root causes, not symptoms. • The architecture, pragmatically. Module boundaries, dependencies, the shared core and the country layers, evolved with clear trade-offs rather than fashionable patterns. • The engineering bar. Code review, design discussions, and mentoring the developers around you, in Zurich and in our Armenia team. Where the frontend ends, the backend begins. Our Product Frontend Engineer owns everything on the screen: the app, Maestro’s interface, the component library. You own everything behind it: the domain model, the payroll logic, the APIs, the integrations with authorities, insurers and banks, and the data. You agree the API contract together, and Product decides what gets built. How we work We are AI-native, operationally rather than as a slogan. AI is how a small team ships like a large one, and how one engineer can hold the standard described here. We expect you to live in these tools and build your own leverage with them: scaffolding, test generation, migration checks, and whatever else takes manual work out of the way. And we expect the judgement that comes with it. AI writes code that looks right and is subtly wrong: a transaction boundary in the wrong place, a migration that works on test data and locks a table in production. In payroll, an amount is either right or wrong. You take the speed and keep the standard. Your first year In your first month, you set up, learn the system and the people, and merge your first changes. Within 100 days, you have delivered the platform’s audit trail, tested and documented, and fixed the first risks you spotted on arrival. By month nine, you are the person the team turns to for the quinn backend, and a developer you mentored is delivering features on their own. By the end of the year, the major back