Software Engineer (Ruby on Rails) in London

About Resi Labs

Resi Labs is the technology and innovation arm of Resi, the UK's largest residential architecture practice. We're building products that help millions of homeowners make better renovation decisions - from understanding planning feasibility and build costs to visualising what's possible with their property. We sit on a unique dataset built over a decade: 2 million planning applications, 40,000 builder quotes, and thousands of detailed floor plans and 3D models linking design, planning, and cost data in ways no one else can. Our products are already embedded on platforms like Rightmove and Zoopla, reaching millions of homeowners per year.

About The Role

We're looking for a strong Software Engineer (full-stack) to join our product engineering team. You'll be someone who thinks of yourself as an engineer first, with deep hands-on experience in Ruby on Rails and a genuine passion for building great frontend experiences. You'll take pride in the quality of what users see and interact with, while being equally capable of working across the full stack to deliver features end-to-end.

As a small, autonomous team, there's a real opportunity to lead here. To shape technical direction, own meaningful pieces of the product, and have your voice heard. At the core of what we build is a large dataset and data processing pipeline covering UK property data. You'll work closely with this data, helping to consume, refine, and unlock its value based on evolving product requirements - so an interest in working with complex, real-world datasets will serve you well.

We're also fortunate to be working on a relatively greenfield codebase with limited technical debt, meaning you'll spend your time building thoughtfully rather than fighting legacy decisions. And we're genuine believers in AI-powered workflows, from how we write code to how the business operates day-to-day, so comfort with and curiosity about AI tooling is a must.

What You'll Do as our new Software Engineer

• Build polished, responsive frontend experiences using Hotwire (Turbo & Stimulus) and Tailwind CSS
• Design and build full-stack features across our Rails application, from database to UI
• Collaborate with product and design to translate requirements into intuitive, well-crafted interfaces
• Build and consume APIs that power both internal tooling and customer-facing features
• Write clean, well-tested, and maintainable code with a focus on long-term scalability
• Work with our UK property dataset and data pipeline to surface meaningful information through the product
• Participate actively in code reviews, giving and receiving feedback constructively
• Contribute to architectural discussions and help raise the overall quality bar of the codebase

What We're Looking For

• ~5 years of professional software engineering experience (we care more about the quality of that experience than the exact number!)
• Strong proficiency in Ruby on Rails - you've built and maintained production Rails apps and feel genuinely at home in the framework
• A strong eye for frontend quality - you care about how things look and feel, not just whether they work
• Comfortable working with HTML, CSS, and JavaScript across a modern Rails frontend stack
• Familiarity with relational databases (PostgreSQL preferred) and writing efficient queries
• Comfortable building and consuming APIs as part of delivering full-stack features
• Experience writing automated tests (RSpec, Minitest, or similar)
• Good communication skills and a collaborative mindset - you can explain technical decisions clearly to both engineers and non-engineers
• Ability to work independently and manage your own delivery without heavy oversight

Nice to Haves

• Experience with Three.js - we're actively building 3D visualisation features and this will be an ongoing and growing part of the product
• Experience with Hotwire (Turbo & Stimulus) and Tailwind CSS
• Familiarity with background job processing (Sidekiq, Delayed Job, etc.)
• Experience with Python and FastAPI - our data pipeline and some supporting services are built in Python, and you'd be expected to maintain and contribute to these alongside the Rails codebase
• Familiarity with Render or similar cloud infrastructure and deployment platforms
• Experience working in a startup or high-growth environment

Our Stack

• Backend: Ruby on Rails, PostgreSQL, Sidekiq
• Data & Services: Python, FastAPI
• Frontend: Hotwire (Turbo Stimulus), Tailwind CSS, Three.js
• Infrastructure: Render
• Tooling: GitHub Actions, Sentry

About Resi

Resi is the UK's number one home extension company transforming how homeowners design, plan and build. With over 10,000 projects nationwide and a 95% planning approval rate, we make architecture accessible and transparent through a digital platform that brings design, planning and build support together. We are a team of ~60 based in the Fora in Elephant & Castle.

At Resi, you will have the opportunity to work differently, take control of, and really accelerate your career. Our success is all down to our wonderful people and their talent, and that's why we treat our employees with the same respect and care as our customers. We pride ourselves in not just aiming to be the best in the industry, but also the best place to work - our collaborative, transparent and diverse culture, with a heavy focus on personal development, means that we don't just grow homes, we grow people too. We have an ideas-led innovation culture and we really care about creating a diverse and inclusive team - so we welcome people from all backgrounds with different perspectives, ideas and experiences to work with us.

We offer our employees:

• A competitive salary
• Hybrid & flexi working
• Private health & dental insurance via Bupa
• 33 days of Annual Leave (including bank holidays)
• An additional day of Birthday Leave after a year of employment
• An additional two days of Peace of Mind leave after 3 years of employment
• Tiered annual leave (1 year per year of service) after 5 years of employment
• August Summer hours
• Work anywhere in the world for one week per year
• Access to therapy, mental health support & coaching via Plumm / EAP
• Gym membership
• Enhanced parental leave
• Regular company-wide socials organised by the Resi social committee, and paid for by Resi
• Office and wider Workspace perks including snacks, fresh fruit and refreshments