Senior Engineer

Why Halcy? Halcy is a travel app built on taste, that works for the entire group. It surfaces the places worth travelling for - restaurants, hotels, bars and experiences - and gets you there. Underneath is the hard part: a whole group planning live, agents that research, compare and act across the travel ecosystem, and a sense of taste that gets sharper with every trip. We want to bring more adventure into people's lives. We're looking for someone who shares that ambition, and who's excited to help build the company that delivers it. Who you (probably) are

• High on curiosity. Low on patience.
• High on autonomy. Low on ego.
• High tolerance for complexity. Low tolerance for repetition.
• Suspicious of process. Religious about pace.
• Knows what breaks and what scales, before it's required.

What you (ideally) bring

• Must have
• 5+ years building production systems, including at least one tour as the senior-most engineer in a small team. You've felt the weight of being the person who knows what could break.
• Deep TypeScript across the stack (React + Node or Deno) and the judgement to make architectural calls without a senior peer to bounce them off.
• Track record of levelling up engineers around you.
• Scar tissue from at least one of: real-time multiplayer at scale, payments and bookings (a travel or marketplace stack), or RLS-heavy Postgres at hundreds of tables. Bonus for two.
• Bonus
• Mobile delivery experience - Capacitor, React Native, or native. We ship to App Store and Play Store.
• Pragmatic on observability and security. You spot what's missing before it bites.
• Shipped agents to real users, not demos. Fluent in context engineering, tool design, agent evals, and the latency and cost of every turn at scale. We route across several frontier model providers; you should have opinions on which does what best.

What you will (mostly) do Hold the product vision in your head and translate it into the technical bets that make it real. Your job isn't to ship features off a backlog - it's to figure out which problems are worth solving and to solve them well. Own the architectural calls that decide whether Halcy works at 100x current load. Concurrency, AI cost, collaborative state, content delivery on mobile. Stand up the operational floor. Observability, error tracking, end-to-end coverage on critical user journeys, structured logging, alerting, runbooks. Build the speed infrastructure that lets the team ship faster as it grows. CI that catches problems before prod, preview environments, automated migrations. The kind of investment that compounds, without adding approval steps. Stay deep in the code. We expect you to ship with your own hands every week, alongside the founders. Architecture without keyboard time decays fast at our stage. Set the bar for our next ten engineering hires. JD, interview loop, onboarding. Be the compass on the calls we cannot reverse. Which decisions lock us in, which of them are worth making anyway, surfaced while they are still open. Benefits

• Compensation €80,000–150,000, calibrated to experience.
• Equity Meaningful equity, four-year vest with one-year cliff.
• Location Hybrid, based in Stockholm.
• Ownership Real ownership over a domain from day one.
• The work An opportunity to solve a universal and meaningful problem.