Founding Engineer

TL;DR

We're looking for an exceptional Founding Engineer to help us define and build the agentic operating system of the future for horse owners and their teams.

You'll get freedom and ownership from day one, taking over the technical work from our current CTO as she steps into a new role.

About HayHay

Horse ownership isn't your average hobby, it's a lifestyle. The typical horse owner spends up to SEK 15,000 a month on their horse while navigating an endless stream of daily unknowns and difficult decisions. Yet the tools available today are fragmented and surprisingly analog.

We built HayHay to change that. Today we're an advisory service putting Sweden's leading horse experts in your pocket. Alongside them is Stella, our AI assistant grounded in the latest equine research. Now we're building the next chapter of HayHay, an agentic operating system for horse owners and their teams.

We're a team of six across product, engineering, design and GTM. The company is backed by long-term investors who know the space, including LRF Ventures and angel investors.

About the Role

You'll build the next major iteration of our product and own the entire technical layer. As our only engineer, your decisions will shape the product for years to come.

To help you move fast, you'll inherit a well-crafted codebase and design system built for efficiency and compatibility with AI agents. Over time, the role and engineering team can grow with you as we scale.

What You'll Do

• Build and ship without the overhead - You'll see your work in front of real users the same day it’s written.
• Own the full technical layer - Architectural decisions, feature implementation, AI integrations, infrastructure & DevOps and code review.
• Make the technical calls - Decide what stays MVP and what's good enough to ship. Understand when speed is the right priority and when cutting corners isn't.
• Shape where we're going - Help define the product roadmap and how we build as a team. You'll work closely with our co-founder (PM) and designer, not just build what's handed to you.

Our Stack

• Frontend – React Native, TypeScript
• Backend – Fastify, PostgreSQL, Redis, WS
• Infrastructure – Render, Expo / EAS Build
• LLM / Automation – OpenAI, Anthropic, Gemini, Pinecone, n8n

Our stack is deliberately built to be worked on by engineers and AI agents alike.

Who You Are

Above all, we're looking for a builder at heart. Someone driven by creating things, who always has a side project or automation they can't help but explore. 

• Strong engineering fundamentals - You think in systems, trade-offs and long-term architecture. And you take pride in shipping clean, maintainable code.
• Technically broad - Comfortable moving between frontend, backend and infrastructure in a single day.
• Built for autonomy - You value the freedom and responsibility of being the only engineer. You're used to owning the entire technical layer.
• Clear communicator - You can articulate technical trade-offs to both technical and non-technical teammates.
• AI-native, for real - You're the one teaching the team about new possibilities, not the other way around. Agentic coding is your multiplier - you deliver at the quality and velocity that a solo role demands.

What You Bring

We care more about a steep trajectory and AI-native instincts than the number of years on your CV. That said, you should recognize yourself in most of the following:

• Fluent in Swedish and English
• Stockholm-based, hybrid (flexible, but we value meeting in our office at Kungsgatan about once a week)
• 5+ years of building and shipping full-stack products (ideally startup or founder experience)
• Strong TypeScript
• Node.js backend (preferably Fastify or Express)
• React Native / Expo (or React and the ability to adapt to mobile quickly)
• REST APIs and PostgreSQL
• A foundation in AI engineering (or the curiosity to get there)
• Cursor / Claude Code / Codex etc. - core to how you work, not a novelty

What We Offer

• Competitive salary and equity, reflecting the importance and responsibility of the role
• Unlimited access to Cursor / Claude Code / Codex etc.
• Fast-paced and hands-on culture, but building for the long run. We're a team that operates on high trust and real flexibility, taking your wellbeing as seriously as the product.

A note on timing: We're reviewing applications on a rolling basis, but we're planning to bring someone on board after the summer. Don't let that stop you from applying, we'd love to hear from you now.