Full Stack Developer

Geniebelt; København; Hybrid; DKK 750,000 - 950,000; Full time

Benefits offered by this job

Hybrid Copenhagen office

25 days holiday

Flexible hours 9:00–16:00

Monthly social gatherings

Job summary

Geniebelt is hiring a Fullstack Developer to join our AI-native engineering team in a hybrid Copenhagen setting. You will work across the full stack, delivering features end-to-end and modernising the platform used by thousands of builders worldwide.

You will ship Backend (Ruby on Rails) and Frontend (React/TypeScript) features, own core product areas over time, and ensure code quality with proper root-cause analysis. You’ll collaborate with skilled engineers in a small, high-performing team.

Qualifications

• 4–7 years of hands-on experience with Ruby on Rails and React/TypeScript
• Solid knowledge of PostgreSQL and relational data modelling
• Comfort with Docker and Git in a collaborative workflow
• Fluent in English and able to share knowledge with the team

Responsibilities

• Backend (Ruby on Rails): Design and build reliable backend functionality and APIs consumed by web and mobile clients
• Frontend (React / TypeScript): Build clean, responsive interfaces that make complex construction workflows feel simple
• Modernisation: Bring the platform to the latest Ruby, Rails, TypeScript, and React
• Ownership: Take ownership of features with support from senior engineers who know the platform
• Quality: Write clean, testable code and perform proper root-cause analysis when things break

Skills

Ruby on Rails

React / TypeScript

PostgreSQL

Docker

Git

English communication

Tools

Docker

Git

Kubernetes

Job description

Are you eager to join an agile development company withno B.S. and no bureaucracy? Do you thrive in a trust-based, transparent, startup-like environment where you are encouraged to have your say and to own the outcome?

AtGeniebelt, we are on a mission to transform construction by accelerating repeatable build. We empower builders to scale excellence through repeatable build: turning every project into a foundation for the next, powered by collaborative, repeatable workflows that drive consistency, predictability, and growth. Our platform handles more than150,000 weekly updatesfor thousands of active users worldwide, and we do it with a small, dedicated company of 11.

We are looking for aFullstack Developerwho is comfortable inRuby on RailsandReact / TypeScript, and who wants to grow real ownership of the product from database to UI, working alongside experienced engineers who know the platform inside out.

Our ambitions are big: to be therecognised category leader in Europe, the#1 platform for repeatable build, and ahigh-performing team with a challenger mindsetrunning a scalable operating model that drives profitable growth. This role is central to getting there.

THE ROLE

You will work across the full stack, shipping features end-to-end and helping modernise a platform that thousands of builders rely on every day.

• Backend (Ruby on Rails):Design and build reliable backend functionality and APIs consumed by our web and mobile clients.
• Frontend (React / TypeScript):Build clean, responsive interfaces that make complex construction workflows feel simple.
• Modernisation:Help bring the platform to the latest Ruby, Rails, TypeScript, and React, retiring obsolete libraries and legacy code as we prioritise stability and a great customer experience.
• Ownership:Take ownership of features (and, over time, core product areas) with support from senior engineers who know the platform deeply.
• Quality:Write clean, testable code and perform proper root-cause analysis when things break.

HOW WE BUILD (AI-NATIVE)

We are building an AI-native engineering team, and we treat modern coding agents as a core part of how we ship. Not a novelty on the side. In practice, that means you spend less time hand-typing boilerplate and more time as aconductor: framing and specifying work clearly, orchestrating AI agents to draft it, and then reviewing, integrating, and merging the result to a high standard. The human owns the judgment and the quality bar; the agents accelerate the throughput.

We are looking for someone who genuinely believes in this way of working and is already doing it, or is hungry to. If you love turning a well-framed problem into shipped, reviewed, production-grade code with AI as a force multiplier, you will feel right at home.

WHAT YOU BRING

• Solid, hands-on experience (roughly 4-7 years)withRuby on RailsandReact / TypeScript. You can genuinely work across the stack.
• An AI-native way of working:you already use coding agents as part of how you build, and you are comfortable being the reviewer and integrator of AI-generated work.
• Solid knowledge ofPostgreSQLand relational data modelling.
• Comfort withDockerandGitin a collaborative workflow.
• Growing systems thinking:you are building good judgment on trade-offs between consistency, availability, and performance.
• Review judgment:you can tell genuinely good code from plausible-looking code. Whoever, or whatever, wrote it.
• Communication:fluent in English, able to share knowledge and support the team.

You don't need to be the most senior person in the room. You will work alongside engineers who have built and scaled the platform, and we will back you to grow into broader technical ownership.

Bonus: exposure to cloud / AWS, Kubernetes, or CI/CD is useful, but not essential for this role.

HOW WE WORK (AND WHO THRIVES AS A GENIE)

Our culture rests on four things, and we hire for them as much as for skills:

• Winning mindset - play to win, know your goals, raise the bar, play the right game.
• High agency - step up, take initiative, own it, get it done.
• Play together - bring your passion, have each other's back, value feedback, enjoy the ride.
• Curiosity - stay open, explore new perspectives, try novel ways, learn fast.

In practice, that means you take responsibility when something breaks - regardless of where it started; you make decisions based on context and requirements, not dogma; and you improve existing code instead of working around it.

BENEFITS & CULTURE

• Location:Hybrid setup in our Copenhagen office(Tuesday and Wednesday are fixed in-office).
• Holiday:25 days of paid holiday, plus 5 additional "feriefridage".
• Flexible hoursaround our core window of09:00 to 16:00.
• Real impact:a genuine opportunity to "punch above your weight" in a small, dedicated team of 11.
• Social:monthly social gatherings and outings with a relaxed, fun team.

START DATE

We are hiring now and would love for you to startas soon as possible.